At least they have a bonafide reason to rappel, that is, to enter a cave. Up at Erie yesterday, I saw a bunch show up just to rap the cliff. That's what happens when you make the anchors too accessible.
I wonder if anyone has ever actually had to wait to get on a climb while someone rappelled it for the hell of it? It hasn't happened to me, but if this "sport" keep growing, I imagine there will eventually be conflicts.