I love theatre because it is literally alive, and live, and living right in front of my eyes. Sure, shows are workshopped and previewed, rehearsed and remounted, but every time I step into a theatre, and every time the lights go down and the actors take their marks, it is the beginning of a new, unique show. Every performance is different, no matter how the cast, the stage manager, and the director try (or don’t) for consistency. Every single show will have a dropped line, a tech malfunction, an inflection, or an improved performance. These are just a few examples of things that make every performance unique, but I think the idea is clear. Live shows are performed by living human beings. Every night is different because every night people are different. This obviously excludes casting flips, and director’s notes, but those two things also contribute to how the performance I saw on a Thursday could be different from the performance you see on the Friday.
Further to the “living thing” point, I love theatre because until the next performance, there are no do-overs. There isn’t an editing bay to cut together filmed scenes. If someone messes up on or off-stage, that miscue is a part of the show. This is not a bad thing. In fact, I celebrate it because in the shows I’ve seen, missteps have led to some of the best comedic moments and showcased the talent of the actors and their ability to seamlessly recover without breaking character. Plus, most of the time the audience won’t even notice.