Because 110% of the time you have your amp maxed up to volume 11 and you simply do it for rock star status. Turn it down to 4 and let the monitors do what they're made for.

You asked.

Maybe you're mistaken and it's singer songwriters that are hated? Those people are horrible.

... only done a little bit of sound work, but in every case, the guitarist demanded that I turn up his guitar to be way too loud relative to everything else. One tried to fight with me once!

2-4k can get particularly harsh.

They hate the guitarist, not the guitar.

Roadies are the salt of the earth, while guitarists are preening ponces.

Because they always turn themselves up way louder than the rest of the band

maybe soundguy's deaf

My hearing is fine---I've always worn ear protection. Almost every guitarist I know has blown his hearing by playing way too loud from his teenaged years onward. This is the source of many arguments, actually, the guitarist insisting 'I can barely bear it!' even though it's pretty near the pain threshold for me, to say nothing of someone who has never been to a rock concert.

There's a reason all of the tickets have riders concerning "loss", and it ain't just about your wallet. Every single rock concert has sound pressure high enough to cause damage.