Costs..
It always comes back to people wearing suits deciding that IT is 'just another set of disposable people', and that everything happens by magic. If you buy Microsoft systems, you're secure, right? Says so in the brochure.. All sysadmins do is press buttons and things happen. Can't be hard, right? Not lke preparing powerpoint slides and presentations where you can actually see someone do something.
HR, having no clue whatsoever, puts keywords in ads, and if you've got the buzzwords down to pat, you get to interview. Unless you already have some really clued in people on the interview panels, you end up with whoever can most confidently throw the most buzzwords in the shortest time (I do interviewing where I work, and the amount of people who confidently spout complete garbage liberally sprinkled with buzzwords, and claim to be MVPs or experienced developers/admins etc. is frankly astonishing. Even when you pick them up on it, they just throw out a whole set of completely unrelated buzzwords).
What people just don't understand is, when you hire a sysadmin, or someone with administrative level access, you're handing them the keys to your company. Unlike almost anyone else outside the directors office, they have the ability, single handedly, to undermine the operations of the company for a significant time period (possibly permanently).
If people started hiring with that in mind, I think they'd be a lot more stringent in who they hired, and HR staff may end up having to get a clue.