I think obvious is in the eye of the beholder, though. I do think if the reasons were spelled out, it might cut down on future violations, because I think the people who have violated the rules may not know that they are the reason the thread is shutting down.
Example: I once had a boss who didn't like to single anybody out. So she would lecture us all at meetings not to drive too fast in the parking lot, to show up on time, etc. And I eventually understood her to mean that BOB needed to slow down in the parking lot, and BOB needed to show up on time, etc. But the rest of us worried that we were the ones doing something wrong, and came unnecessarily early, and drove unnecessarily slow. But Bob, who was obviously oblivious to the rules anyway, assumed that she wasn't talking to him, so he still showed up late and drove too fast.
In other words, sometimes I think we'd be better off if the mods said "OP, this is a rant so I'm locking it" so the OP won't post ten more rants. Or "Posters A, B, C and gollymolly, I'm closing this thread because you can't discuss the topic like adults" - so that A,B,C, and I can understand that we've done something wrong, and posters D - Z don't worry that it's their fault and start walking on eggshells.