I believe that you are making too many assumptions about "fools" who "follow the barking orders".
First of all, there is a question of etiquette. A person who is considering training with another sifu, should at least pass it by his own sifu.
Secondly. People can't just run along and train or cross train in anything they wish. Presumably if you are training a TCMA, you are doing so with an expert. It is always good to ask their opinion about what you intend to train in, because there are cases where people seek to train in another style that has contradictory principles and concepts to the style they are currently training. So, if they have not got their core style into their "veins", then such cross training can result in the unnecessarily hindering of their progress.
Of course, this is no problem for people who are ignorant of a given TCMA style's body unity, rooting, etc. principles to start with, and are happy to treat any "kung fu" training as a type of glorified kickboxing.
It is never too late to learn manners!
You are making a huge assumption. You can't just run along and cross train in anything you wish if you are practicing a given TCMA style. Asking your sifu, may even result in him recommending you to cross train one style, as opposed to another, as that style will be complimentary to the core style you are training with him.
Moral of the story is that etiquette can be beneficial to personal evolution.