Why Wing Chun teachers teach multiple arts

If Wing Chun is so great why do they teach other arts too ?

  

· Does the teacher teach more than one art? They are usually making up for lack of knowledge by adding other arts. Jack of all trades, master of none. This is important to understand, NOT ALL ARTS CAN BE COMBINED SUCESSFULLY! Sure it sounds great, “I took all the best parts of each martial art and combined them into one” This idea preys on ignorance. It is the martial arts equivalent of buy low, sell high in finance. Sounds great if you don’t think it through. Did they learn all those arts completely or were they just students who got bored and wanted to be in charge [EGO] and collect all the money [Greed]? What makes them think they have the ability and knowledge base to do that in the first place?