Most people's first view of wing chun will be from youtube. Therefore they are likely to see the following:

1.  Someone performing a form (kata) on the spot, with maybe a bit of body rotation.
2.  Chi sau rolling followed by a flurry of punches.
3.  A student throwing a stiff armed punch to a Sifu who takes his head off.
4.  Sparring which looks like kick boxing (no resemblance to the above).

Let's look at this in detail.

Forms
The forms are important as they give us an idea of how a martial art is built, they set a criteria for its principles and limitations.  A lot of time is spent practicing forms, so a good way to judge someone's understanding  of the art is whether they use those movements in application with a non-compliant partner.

My belief is that the originators of martial arts such as wing chun were the outstanding fighters of their day.  If they lived to a retirement age they would have been inundated with requests to teach.  One option would be to choose one or two rich students to pass on the art and rely on them for financial  support, the less risky would be to open a school.  The problem with a school is keeping a group  of students busy for a long period of time. What is likely is that after a period of persistent questions ('what technique was that sifu', or, 'can you show that again'), the teacher would have realised it is easy to perform his favorite techniques in a form which can be passed on.  Over time those forms would passed down through the generations as if they were sacred, but they are in fact only the outward expressions of an individual long since dead.  With luck some time later a student will grasp the essence of the movements, adapt them for themselves and the art will move on.  This  happened in arts like tai chi where the Chen style begat the Yang style which begat the Wu style etc.  Small changes were made by great fighters to suit their own style, to return the art to the status of a fighting style again.

Yip Man changed the wing chun forms to suit himself, they are important as they teach us about his interpretation of the art but it is the principles of the movements which matter and not precise angles etc. Keep in mind that Ip Man was about 5 foot 1 inch tall, his tan sau will in application look different to mine or your unless you are very short.

Chi Sau
The number one problem for wing chun is also its number one attraction.  Chi Sau is addictive, it is fun, it feeds the ego and it give the impression of improvement.  Once a student starts to practice it they usually get lost in it and stop seeing what it is they are doing; a game divorced from reality.  The truth is that if both parties go at it 75% they get a good workout, take a few hits and give a few hits and the good fun is had by all.  Problem  is that when it comes to reality and someone comes at you with 100%, the wing chun based on arm manipulation might fail under the force. The other guy does not respond in a wing chun manner and panic hits.

The chi sau  rolling action done by most wing chun practitioners is a method less than 100 yards old, much younger than the art itself.  It was probably taught to Ip Man by Yuen Kay San who may have invented it (much debated). Other non Ip Man lineages do not practice by standing facing each other in the same manner, it is done side on and the arm action is closer to tai chi circling.

As with forms, chi sau is a great way for the teacher to keep the students busy in class. However as the techniques taught get more elaborate, the objective gets more obscure and eventually lost. Great fun is had chasing hands, students get good at chasing hands  whilst the outside world watch and wonder what is going on.

Demo's
All I would say is everyone sees through these so please do them properly (just read any comments on Youtube).

Sparring 
Fighting is fighting, the objective is to put the opponent in a position that they can no longer be a threat to you. The first question you need to ask yourself before fighting  is have you learned anthing in your form practice and chi sau which will assist you. Unless you are considerably biggest than your opponent,  I would suggest the skills of pulling someone's arms down, holding onto their wrist and slapping their forearms are more likely to get you in trouble.

The forms are there to help you to understand  how to generate relaxed power, chi sau is there to practice generating power under pressure.  Get these ideas right and as soon as you touch an opponent they will feel your mass as a threat to their whole body. Like chi sau, extended sparring sessions bring out the fun element, a martial art of play, but if the idea is right the focus should be on dropping our mass into the opponent as quickly as possible.  Not an easy or comfortable thing to practice.

What should wing chun training look like?

1. Lots of standing; understand your body.
2. Lots of form practice, understand what happens when you rotate your limbs and how it affects your balance.
3. Have a partner test your movements in a compliant manner.
4. Have a partner test in an uncompliant manner.
5.  Chi sau to understand rolling as a form of simultaneous offence and defence.  What this means quite literally is every movement is both a simultaneous offence and defence. If you disengage contact to slip a hit in, you are not defending  and it is not good wing chun.  If you defend by attacking the wrists or pushing sideways, there is no offence to the opponents body and it is not good wing chun.
6. Gor sau to attack and  break an opponent in as short a time as possible.

If at the start of the journey we deviate in the wrong direction,  by the time we realise the mistake we may be further away from the goal than we started.   It makes it hard to enjoy the journey when you are always looking for shortcuts to catch up to where you believe you should be. 

You cannot have an interest now a days which has not been commercialised.  Fashion, sport, music art etc, anything new is taken apart, packaged and sold back to us.  Football (the beautiful game), the Olympics; they are now just ways to cynically extract money from us and exploit our passion.  A good example is barefoot running, once this became popular Nike started selling specialist thin soled trainers for £100, the irony being they invented thick soled running shoes which are supposed to do so much damage to our bodies. £100 for a label and a bit of plastic.

Art is supposed to be different but even there the individually is stripped away, catagorised and cleansed of uniqueness. 

The true beauty of these interests is that when we engage in them ourselves, play football, paint, make music etc, the joy becomes ours and is  much better than observing.  We do not need to be ranked, measured or critiqued, joy comes from doing and not analysis .

Why internal martial arts? 

With an internal art we are not looking outside to be judged, for a certificate to prove merit, the interest is in knowing what we are capable of. Understand your body better, let it move naturally and we get the outcome we were seeking without the effort. Like any art it takes honesty with yourself, a teacher points the way but once you know what you are capable of it is in your hands how you develop and ultimately what you will achieve.   My recent experiences in practicing/teaching with people who have trained in other wing chun lineages, is that they have been taught to crudely copy movements without any concept of why they are doing them. Even a decade of train like that will get you nowhere.

What has this got to do with commercialisation?

People will try to sell you uniforms, gadgets, books, secret methods etc, but ultimately you are your own laboratory of experimentation. The real investment you need to make is working on yourself in training. I own four guitars, but that does not mean I am any good at playing them, my youth was spent dreaming of the playing on a stage as opposed to practicing.

Effortless is actually the result of a lot of effort, just ask any martial artist, sports person or musician.  The trick is not to  concentrate on the desired end, but enjoy the journey and the results will come naturally.