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.
Hiking and basic wilderness knowledge.
I live in the Mojave Desert. Simple stuff like knowing not to cut through bushes, wearing proper shoes, avoiding feral dogs, and always having something to defend yourself with when walking in the desert aren't common among a lot of people who aren't originally from here.
What do you delete yourself with in the desert? A water bottle?
Just select yourself and hit that back key