The worst thing about this job is that it forces you think of everyone as stupid and incompetent FIRST before they prove you wrong.

That’s right. That’s what you see the most of on helpdesk or even as a sysadmin (because items the helpdesk can’t solve bubble up to you). So your experience is an endless cavalcade of human stupidity. And just as with retail, even though the vast majority of people are not actually clueless clowns, nearly all that you directly experience are in fact fully dressed as Ronald McDonald.

And as with retail (again), it makes you terribly jaded and misanthropic. Any IT person who has done helpdesk or sysadmin becomes a bit of a jerk for a good damn reason.