Despite what you keep implying, Floyd, my homework's pretty up to date. I've been playing for longer than you, and along the way, in addition to other venues, I've seen the inside of plenty of bars on a couple continents. In some times and places, what you imagine to be universal actually holds true; in others it doesn't. It's true that if a cover band playing rock standards has their noses stuck in their music stands and plays with marginal competence, that tends to go over badly. Even then the music stand isn't the core problem--being wedded to it, having no stage presence, and sucking are the problems.
That said, beyond serial bar-band monogamy, it's a big world full of enough strange practices and subcultures for a university full of anthropology grad students to write dissertations on--as you probably know. I'm assuming that playing as long as you have, you've probably seen more variation than you're letting on. You on the other hand seem to be assuming I'm an idiot. I *know* that your assumption is wrong, and it's possible that mine is, too. I'd prefer not to think so, though.