hey
There are occasional reasons for DJ's to "mime" publically, usually when its a high profile, very tightly timed TV events like MTV awards and big half time stuff. As well as risking the DJ making a mistake or playing too long, your also just risking thinks like equipment failure or a skipping CD/Crashing Laptop. Better to be safe than sorry when there are X-million people watching, I know I would!
However that said, being a musician as well as a sound engineer I do appreciate and somewhat agree with life's constant arguments about mimers vs musicians. But at the end of the day its about draw. Its a business and it works very clinically.
A persons name will draw in X amount of people/ticket sales for the promoter, and so the promoter will pay him/her an appropriate fee so that they can secure that acts services and still make a decent profit.
As long as all those people that turn up have a good time and think they enjoy themselves, it shouldn't really matter. If they don't then people will stop buying and promoters wont book or drastically cut fee. Simple market forces.
If you could get paid 11million for standing there doing nothing then you would, no problem! Sign me up tomorrow!