I've seen seen beginners bring .22LR pistols to the Illinois concealed carry qualifier (.22s are allowed) they've either never field stripped/cleaned/lube cleaned or cleaned but then (a) oiled the whiz out of 'em or (b) not lubed at all.
Invariably, those guns start to have feed problems.
Fortunately, a quick field strip, a spritz of whatever CLP product is handy and some quick work with a toothbrush and a rag will put 'em up and running.
Also, I've seen revolvers gunked up at the crane, the latch, the ejection rod, etc. Some were in like new condition, just over "cared for" and stored poorly.
All guns aren't ARs, and some are less tolerant of improper care than others.
Gun care is not a huge hairy deal, but I think especially among beginners or the non-enthusiast, there is some apprehension about it, and they tend to use either no lube product or too much or some "wonder" solution that isn't.
There's certainly a sweet spot, IMO, and it's moderate, usually modest, lubrication.