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.
Apparently there have been issues when US and British forces have worked together before du to the “I thought you were exaggerating” mindset.
The brits have a tendency to downplay really bad situations to the point where, “It’s actually quite chilly” means “We’re in deep shit”. I read somewhere that this caused serious miscommunications several times, because Americans didn’t understand that brits were downplaying things, while brits though the Americans were always exaggerating.