Film is a recorded movie and it will always be the same, no matter what or how many times you watch the film because there is no constant change.
Theatre, however, is sometimes a constant change, there are understudies that need to be filled in and that understudy gives off a different vibe than the originally casted member in the show. There might be accidents, etc. Audience will always change as well since it almost a different show each time, say for instance today the performance was great, but tomorrow, they need an understudy to cover and it gives a different vibe. Every person casted in the show is usually comfortable with who has usually played in the show the most and constantly interactive and there are no "CUT!" or any redos, and have to continue on with show.
