I have also been registered with several improtant institutions at an address that does not exist, because the telephone operator made a mistake - and the address was preposterous, they have put me in a house number 15000. So they don't check much.
Thirdly, addresses are not real. They are a myth, like simultanous events in special relativity, they do not exist in the real world but people who never had to deal with them much don't realise it.
What we call an address is a set of instructions to the postman, and if that set of instructions gets the post to your door, it is valid. Anyone paying attentions should have noticed that they often recieve post with slightly different permutations of their address. And ofcourse I have given a few silly examples. But there are genuene addresses that are unkowable. I lived in a building that spaned 3 streets, (one for each side, the last side was a house). It had 2 entances and 2 addresses.
There are addresses that are not a {street}{housenumber}, there are addresses that are a grid and no map software knows how to deal with them
And lastly there are houses that have no 'official' address! A lone hamlet near the coast might have no name at all.
So the only way to determine if an address is real, is to sent a letter, and to see if it arrives.
In the US, a lot of addressing was rationalized to support E911 service. So for example, a "camp" (i.e. a cabin without utilities) I would sometimes rent used to just have a name. But at some point it got an address on the dirt road it sits on. They also did things like change a road segment name if there was a gap between it and another segment with the same name.