I wear glasses and seem to still be capable of moving my eyes.

Unless you wear bifocals. Single-vision lenses have a usable field of view that is as large as the comfortable range of movement of the eyes.

Anecdotally, I started wearing glasses a couple months ago and have been annoyed at how often I have to adjust my ahead when I would have normally just moved my eyes. My glasses tend to slip down my nose just a tad which cuts off a non-negligible amount of FOV.

That varies wildly by the design of the glasses. I tried rock climbing once with my glasses instead of contacts and it was intolerable. It wasn't immediately obvious how often I relied on a quick flick of the eyes to the outer edges until I tried it.

As to the original point, people adjust their head position all the time without even thinking about it. It's an unnatural and conditioned response to hear a noise on your right rear and move a joystick or mouse to look for the source of the noise.

It's perfectly possible to buy glasses that only minimal obstruct your field of view, and let you look at things out of the corner of your eye.