Lesser restoration (5e 2nd lvl) can cure blindness, but I'm not sure if it can restore destroyed or removed eyes. So it would depend on the kind of blindness, and if it was at all magical in nature. That and from a few threads the estimate for its cost is around 40 gold. For a lot of "commoners" their income is anywhere from poor (60sp) to well off(1gp) per month. So I can easily see many mid tier peasants not having the money to have lesser restoration cast on them. Especially if they live in some tiny village where there isn't a temple in town, like you would have in a city.
Even in a city if the head priest is high level, and has say, 4 other actual clerics in the building not just priests, thats 18 casts of lesser restoration (wasting high lvl slots on a lvl 20 cleric) and maybe 5 per 5th level cleric. So 38 a day. In a city with tens of thousands of citizens with many myriad medical issues. Sure maybe there are 4 or 5 temples, but its still just a numbers issue at some point.
The dnd economy is a bit wonky and its magic system is difficult to match with the world sometimes, esp high magic settings, but I think the sheer scale of the population of commoners and non magic users sort of makes it pretty understandable that disabilities would still exist everywhere except the very wealthy or capable(adventurers themselves).
This of course all depends on what level of magic you have in your world. If it's very high magic then maybe there are a lot less disabilities, but those that exist are less "im blind from basic eye deterioriation" and more "goblins tore my eyes out as a child and it'll take a decently capable cleric to fix this, and also I'm blind so I make very little money so I'm SoL"