When you are part of a production, you have some down time, but not a lot. If you start a conversation in this down time, the chances of you getting called to the stage or hearing your cue are pretty high, in which case you need to bust your bottom to get there as quickly as humanly possible. This means we are all pretty used to dropping a conversation mid-sentence and running off.
The bad thing is that I've started doing that in other social settings. Perhaps someone is talking and I hear something else that catches my interest....off I wander. Oops. Gotta work on that.