I think magnet school and/or outside school /rec-league sports can easily bring that 15h number.

Overall I think you are right it is indeed bubble and once one is in, it is difficult to see not everyone is doing that.

I have a friend in town both husband, wife work from home and extremely busy with their elementary/middle school kids school/activities that I haven't seen him in years.

Being out of their bubble I only know whats happening but don't get to be tutored in how all these activities are essential. And even rare back out once in a while can be serious digression that affects child's future.