I think this is pretty true for every really big city I've been to in Europe - such that I wonder if it's a city size thing rather than a location.
Trying to talk to random people in London you get weird looks. A small town further out in the country, hope you're not in a rush as they'll talk your ear off.
I don’t think it needs "really" before "big", it’s certainly not normal in the big city I live in now (pop 200k) nor the medium big city I lived in before (pop 90k). I can believe it’s like that for small villages, idk, maybe pop 1k.
I generally said hi to people in a ~50k pop city, and would regularly recognize people by face even if I'd never spoken to them before. Certainly in the ~1.5k village I grew up in you'd know most people, again if not their names, and would always say hi.
But in that city there were still multiple "centers" - the local pub, couple of shops and whatever - Being the European style town that was actually like 15 different villages that slowly merged. Perhaps because of this it really acted as multiple smaller towns in many ways.
There's probably quite a big variation based on local culture, density and other things, but I'm pretty sure it's a trend by size.
Trying to talk to random people in London you get weird looks. A small town further out in the country, hope you're not in a rush as they'll talk your ear off.