But, assuming most people aren't complete morons and can actually do stuff if they decide to sit down, Google how to do it and actually do it instead of declaring "I am stupid" and not even try

Extremely charitable assumption, I'd say.

I do think most people do in fact possess the ability to follow instructions and succeed at installing Linux from USB. But it all falls apart at the key word "decide". Very few people choose to devote the low, but nonzero, effort required to pull it off.

for linux specifically the hard part is entering the BIOS to disable secure boot and then go into the boot menu to select the USB

I would say, for the demographic I'm thinking of, the hardest part is actually getting the installation media in the first place. Not because it's challenging to do, but just getting over the mental barrier of this (to them) extremely unorthodox method of installing software.

Like, first you have to find the thing and download it. Which, fine, that's typical so far But the thing you download isn't some .exe you run. No, you need to put it on a flash drive. So you need one of those lying around, either empty or with nothing important on it. But you don't just copy the installl file onto it the ""normal"" way, nooo... you also have to separately download some strange utility that burns it onto the flash drive in some special way or else it won't work. Only then do you have to tickle the BIOS.

I understand if you or anyone else reading rolls their eyes at that description because these steps are so boneheadedly simple. And I agree, they are. But it's not so much a question of whether it's hard to do, it's a question of whether it feels safe and natural to do. Which, to you and me, it is. But to the kind of person who, as you say, shouldn't even be using a computer in the first place (but they must anyhow, because trying to live in our modern information age society without one closes too many doors), it's an uncomfortable, dark ritual.