With films, they do not work continuously, but have lunch breaks, or do the same bit over and over. It must drain them to have to put all of themselves into a film role, and be interrupted all the time.
A live theatre part goes for a few hours, if a major role, and they can really be that character.
Sure, when reading a book we also put it down to do something else, and I hate that. When I am really interested in a book, I don't want to stop! But if I read it too quickly, then I miss it when it is finished!
Before TV, in some good families, like a hundred years ago! - the father (by oil lamps) read aloud for the mother and daughters, who of course embroidered. What the sons did I am not sure!
In my family we sometimes all listened to a play on the radio. Not that often. My dad read the newspaper and did the crosswords, I did my homework. Can't remember what my mum or sister did.