As a nation, I'm not sure what we can do. It's very hard to legislate common sense although the politicians always attempt to do so.
I agree with your assessment. I'm a little older than you but it was the same when I was a kid. We were told to go outside because it was too nice of a day to stay indoors. We played football or stick-ball in the street. Rode our bikes all over town. That does not happen any longer. Why? I don't really know. Some of it is due to everyone always being on the go. Precious spare time for adults to share and spend with their kids. I also think some people are skepitcal of letting their kids ride all over town on their bikes for fear that something bad will happen to them.
There are many causes and probably just as many solutions. But I'm overweight, as those of you have met me can attest to, but it aint someone elses fault, it's all my fault. I got myself in this predicament, but now I've got to get myself out of it. I need to pick myself up by my bootstraps and do what needs to be done. Too many people now take no responsibility for their actions and that can attributed to alomost any activity.