Because kids had to use their initiative and find other things to do. When I was growing up places like Heath Park, Pontcanna and countless other outside locations were populated massively by football teams on a Saturday afternoon. Now there are hardly any teams as kids prefer to stay in their rooms playing computer games and such like.
I can only speak from personal experience but at a young age I was out of the house from 10am until at least 5pm. Now kids can't go anywhere without parental supervision. That's not a criticism by the way but a reflection of current society.