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.
i never been to australia. For me as a good swimmer even as a kid the flags at the balticbsea cost meant nothing. my sports club would regularly go for a camp at the balticbsea and the stronger the waves the more fun we kids had. With such a background that the flags are just a hint for old and unsporty people, it is easy to underestimate the ocean.