I don’t know how you can quantify how many people, but some surveys put the number in the general population to between 60% to 75%, so I don’t thing 25% to 40% is a tiny minority. Within the frum community it seems a higher percentage (can’t really tell who is wearing contact lenses), but maybe it’s genetic among eastern European Jews or maybe from studying so much
I’ve read but don’t recall where that it’s not from the small print but from SWAYING when davening/learning which unduly strains the eyes that need to focus.
i believe r’ isser zalman bought a ray’ah from a gemoroh in bechoros that people saw much further (it tooks there how far a sheppard could see his sheep – i don’t remmember where) . he suggests using artifical light (including candlelight) ruins our eyes. he says that the bedouins see better since they don’t use artifical light.
I think its from all the addiction to technology. your eyes are glued to a screen 24/7 and they don’t want to see all the shtus so your eyes weaken to save your neshama. its a chessed. say thank you.