How many people would come to hear/see those bands if I wasn't there running sound? The point is, if I am being paid by someone other than the band, my reputation is every bit on the line as yours.
And, again, I am only playing devil's advocate here. I get along with everyone I work with (OK MOST everyone I work with). But I completely understand some sound guys having a chip on their shoulder. It's as though some musicians show up to the gig breathing fire and spitting nails just LOOKING for a fight with a sound guy. It's as if even driving TO the gig some are thinking "If that muther ****** slams one of those generic ******* DI boxes on MY ******* stage at MY ******* gig I will rip his little head off and piss down his throat! This is MY sound. He can live with or else!" And if you come at ME with that attitude, I will be a little less than cooperative right back at you. And it may be YOUR gig, but it's MY $50K worth of gear. I assure you that way less than 1% of you here have nearly as much time, money, and effort invested in your craft OR your gear than I do. So don't hand me "I've been honing my craft for 15 centuries and know what I want and I know what sounds good." I'll get you there. Don't worry. Nobody wants you to sound amazing more than I do. Hooking up hundreds of cables, setting hundreds of dials slides and knobs in exactly the correct position, and having a band sound HUMONGOUS and CLEAR is fun for me. ESPECIALLY bass players. But put your attitude in your pocket or I will make getting there ZERO fun (and lose ZERO sleep over it).