For me it’s the paranoia surrounding webcams. People outright refuse to own one and I understand, until they go on and on about how they’re being spied. Here’s the secret - unplug the damn thing when you think you won’t use it or haven’t used it in a while.
They, whoever it is, can’t really spy on you on something that’s already off and unplugged!
They don’t “often come with” I’d say it’s fairly rare, and especially in the last generation of computers that most have now.
Also, what you mention are all steps above and beyond OP’s direction to “just unplug it” and they come with compromises - I.e. A shutter cover isn’t a HW disconnect, two very different things. And, a sticker isn’t really removable temporarily when you actually do need the camera deliberately. Certain high end laptops have a purported physical HW disconnect toggle or even some “flip around” cameras that are only deployed when needed, but again, few and far between.
Sorry if I was wrong about the prevalence of such protections. My perception may be biased because the notebooks used by our company are all equipped with a switch or shutter of some sort. (HP brand, IIRC) Regarding your second point, however: surely a shutter physically obscuring the camera lens is just as effective as disconnecting the camera when it comes to protecting the user’s privacy?