The studio didn`t ask them to learn their trade, they just worked them, and when that personality or that gimmick or whatever they had ran dry at the box office, they were dropped and out.
So whatever I might have started to learn at that age was all undone by the next director and next crew in the next cheap picture, because I was allowed to get away with murder.
There was only so much television you could do.
Source: brainyquote.com