I think it's because old games are harder to find than old movies. And they run on old hardware that is even harder to find. So you have to emulate, and sometimes it's hard to find the game you're looking for.
While with movies, every generation of media, they re-release the old movies on the new media:
>The film was released on Blu-ray disc September 13, 2011, for a special 70th anniversary edition.