Stage actors are usually much more conscious of speaking up...

Stage actors are usually much more conscious of speaking up and making sure that everyone can hear in the back of the theatre; a film actor probably thinks of that a little less. Unfortunately, there's a style of acting going round, especially with the younger actors, where they talk without even moving their lip. Maybe it's because my hearing probably isn't what it was 40 years ago but I'm sitting there going "What did they say"?