Too much time in front of a screen.
Mostly correct I think.
The problem is a solution is so readily available with glasses, contacts, and reading glasses/cheaters... hear me out on this. I'm into optics more in a scientific sense but I'm interested in the optics of the eye too. Your eyes are like any other part of your body that get better with training or gets worse with not being worked. The eye is more or less elastic and muscles contract to elongate the eye so your lens can focus the image on the retina. If you don't work those muscles they become less effective, further if you don't "flex" your eye it becomes less elastic. Double whammy, and corrective lenses exasperate this further by making you not have to work at it to focus on something.
A couple years ago I noticed my near vision was going, not being able to focus on something very close to my face. Something very typical with getting older I was told. I started working on it, I don't know if you could call it exercises or not but I got it all back. I've also reduced my prescription by 0.75 diopters over the last couple years and I'm expecting another 0.25 drop next time I see my optometrist. I think if people worked at it they could make their vision better and require less correction in their lenses, instead the trend seems to be to add more correction so your eyes don't have to do anything to focus.