I was thinking about that when I was dropping my 6 year old off at some hobbies earlier - it’s pretty much expected to have learned how to ride a bicycle before starting school, and it massively expands the area you can go to by yourself. When she went to school by bicycle she can easily make a detour via a shop to spend some pocket money before coming home, while by foot that’d be rather time consuming.
Quite a lot of friends from outside of Europe either can’t ride a bicycle, or were learning it as adult after moving here, though.
edit: the high number of replies mentioning “swimming” made me realize that I had that filed as a basic skill pretty much everybody has - probably due to swimming lessons being a mandatory part of school education here.
It also has to do with the wide diversity of languages spoken. The elementary school where my kids go put out a statement during the pandemic that there are 32 different languages spoken by kids at home. They had gotten many requests for school communications in more than just English and Spanish, and had to explain why that wasn’t feasible.
So there are a ton of bilingual kids in their school, but my kids could learn the 4 additional languages spoken by the kids in their classroom, and the following year they would need to learn 4 entirely new languages. They learned to count to ten in several languages, but like you said, they will never have the opportunity to become fluent if they don’t go somewhere less heterogenous.