At what point did people begin to play different people in each film?

people back then where contracted to studios, and this also meant that they could only do certain films (even then, the studion would pick the films they could star in) this meant that actors were typecast (cast in to playing certain sterotypes) however today, actos are not contracted to studios and they have there own choice as to what they want to do. the reason typecasting is bad is becuase it looses you money in the long run,, e.g. take a look at sylvester stallone, he was a big action hero, but now he is too old for such roles but because that is all he has done he cannot find work... probably the reason he accepted the pathetic scripts of the latest rocky film.