It's the same in Europe with the 5-stars-is-normal scale.

In my personal experience it's the app that fosters it. Many companies who ask for reviews follow up anything below 5 stars or 10/10 with "how can we improve?" Or some similar questions. This is friction they generate for me as a user if I rate anything below top tier.

Personally for me 5 stars or 10/10 would be service that is so good I couldn't even tell you how to do it. I couldn't tell you how to improve to that state unless the business in question is something I'm very familiar with. Still I sometimes find myself handing out 5 stars because otherwise I have to find something to complain about and I just can't think of anything.

So that is what has made 5 stars for me go from "mind blowingly outstanding" to "nothing to complain".