Alex, it's a tough call really. A major part of it (in my opinion) has to do with what Jeff mentioned as well as what sharke's belief about the "deaf" thing. The room is soo important in this for sure. Another thing to keep in mind....when they soundcheck, the place is empty. Add some people in it and the eq's you were happy with 4-6 hours earlier no longer hold true. Especially if the columns/speakers are not in-air and the soudman may have been partying a little before the show.
Ever mix in a club with people standing in front of your speaker rig? That totally changes the listening experience for others as well...and what do you do, jack up the highs because people are absorbing the sound that are up front and kill them with highs, or leave the mud? Depends on the room and the situation, ya know? That's another thing too..where you are seated/standing. Some rooms have a very focused sound and have sweet spots where you just may not be.
Agreed also on things being WAY too loud. That said, I sincerely believe things are lower today than in the 80's and earlier. And those soundmen knew how to deal with loud music. I remember seeing Van Halen for the 1984 tour...they were so loud, there's a V and an H embedded into my forehead. LOL! But they sounded great even though it was really loud. Rush on the Signals tour was so loud, I couldn't feel myself breathing. My ears rang for 3 days after. But again...excruciatingly loud, but a well mixed loud. Even Terrible Ted Nugent was unGodly loud...but it sounded great. Those dudes just knew how to deal with it better than today's soundmen in my opinion. I believe some of the soundmen are trying to use studio techniques on their live mix by using loads of limiters...and they are failing miserably.
Just about every show I've either played at or have been to, the soundmen have their lappy's and plugs running. The first thing I do when I'm playing in that situation...is I make them kill that stuff. It just doesn't sound right and turns everything into loud, mud.
Also, lots of soundmen just don't have a clue about how to mix in certain rooms. As you know, it's not easy in some of them. The worst is when all you hear is kick and bass and the guitars sound like little bee's buzzing around because they are eq'd horribly and the soundman doesn't have them up loud enough. Which brings me to the next possibility....
The band being too loud. The worst offender in poor sound is a band that is so loud, you either have no control over them or you just totally kill them out of the board. The lower you are on stage, the more control you give your soundman as well as the lack of raw, uncompressed stage volume hitting people in the face. Sure, most rock bands need a little stage push volume wise...but man, some of the stuff I've heard is so insane, it can make a great band sound amateur.
It's funny man...when I show up to play my big shows, I'll usually bring 4 Marshall cabs. The soundman takes one look at me and says "oh brother, here we go...another one of THEM." Then I fire up and play and the dude will say throught the talkback mic "dude, are you kidding me? I never thought I'd ask a guitar player with 4 Marshall cabs this...but can you please turn up?" LOL!!! I usually respond "do I have to?" to where he says "you can't be serious...are you ill? A guitar player that doesn't want to turn up...ok, now I've seen it all." Hahahaha! I just hate raw stage volume, Especially me being the singer in my original band. I'm a singer, not a screamer. If I scream it's for effect purposes, not because I can't hear myself over the band. So I would say this is probably the #1 offender...bands are just way too loud to where the soundman just has no control over them.
If you do that in a club around here, they'll throw wet napkins at you. If you keep doing it, they'll get some powdered hand soap, use a little water and make it into a ball, wrap it in the napkin, wet it a little and whack you with it. You definitely turn down after that...or dude will kill the power. LOL! :)
-Danny