What are urban kids supposed to do, play in traffic?
There is no outside.
There is no outside.
Of course, there are far too many drivers who view anything that impedes high speed travel as a nuisance, or worse. I regularly see drivers who run stop signs in front of a school, drivers passing unloading school busses with their stop signs extended, and impatient drivers try to push through crossing guards as children are crossing. I have also known crossing guards who were struck by motorists. Things like traffic calming measures don't work, since it typically ends up with drivers being more reckless. Very little seems to be done about it, aside from periodic campaigns (typically at the start of school years). And, of course, punishing children by limiting the spaces they can use and independence.
People often claim that the cycling culture of the Netherlands was a product of trying to protect children from traffic. Most of the rest of the world, including England with it's "no ball game" signs took the opposite approach: rather than addressing the problem, they punished the victims.
It may be worse for a rural kid. All that countryside that surrounds you is private farmland. Of course, now and again, you trespass and earn stories of being chased off by dogs and puce-faced-shotgun-wielding arses but it's not your daily hang-out.
Truly public land (not just a public pathway) will be concentrated in nature-reserves and odds are it will be out of reach except for special adventures.
The village-kid hang-out is typically "The Village Rec" (recreation ground) but if you live in something less than a village, i.e. random splats of houses between villages, you end up living half your life at a bus stop waiting for the mercurial 2-hourly bus service before you can even see another human face.
Instead, we see the same problem everywhere, including places in Europe and Japan where the outside is just fine.
When our parents were kids, everyone drove but all the kids played outside.
There are also location-specific effects. The happiest few years of my childhood - I'm a generation older than the over-scheduling thing; we were latchkey kids, as they said then - were spent on a block with three other families whose kids were +/- three years of me and my sister. We were on our bikes, or building forts, or playing football in someone's yard every single day. Then, the course of a year or so, the other families all moved away, and... Well, I was sedentary, reading books, and lonely for the next few years.
(A lovely coda: a few years ago I happened to visit the city where my favorite friends from that period had settled, and looked them up. We literally had not seen each other in twenty-five years. I thought it might be awkward, and maybe for thirty seconds it was, but we immediately recaptured the tenor of our ancient friendship, and it was magical. I see them every couple of years, now, and am so happy they're back in my life.)
To pull those two points together, when there were enough young families (and higher population density) that there were kids on every block parents didn't need to schedule their kids social lives. Now that the fertility rate has dropped, and housing sprawled, that's often necessary - and even when strictly-speaking not, it's become a cultural default that's difficult to overcome.
I'm not going to do that, unless they explicitly ask. Would rather multi-sport and have them try other things including music.
Even if there is a motorway in the way there is often a bridge or some kind of underpass.
In urban areas there is usually a park/playing field 5-15 minutes away
And if there were, whatever they might dream up to do with outside would be rapidly banned.