Life’s ironies, or why do we pay actors to do things kids do for free?

I was reading a typical adulatory actor article in the New Yorker in which an actress was highly praised for her portrayal of Temple Grandin in a biopic, especially for the way she had captured the specific mannerisms characterizing Grandin’s behavior.  I remember attending school with several really good mimics, and if they had pulled anything like that, wouldn’t they have gotten into big trouble for making fun of the weirdo? Yet any one of those kids could have done the job just as well as the paid pro, for sheer love of the art – of pulling it off.