When I was 9 or 10 during summer, I spent 12 hours a day out of the house running around in the woods and generally finding ways of entertaining myself.
Now, I freely admit there is more to keep kids active inside these days (we had 3 channels, 2 of which were very static-y). Between video games, computers, the internet, and a bazillion channels, there are lots of ways for kids to keep themselves distracted without going outside. But that does not explain why so many people seem to think it absolutely absurd to see a kid walking down a suburban sidewalk alone.
When my kids were younger, I was met with incredulity and shock when I noted that our local middle school is less than a mile away and there was no reason they could not walk there if they needed to. You would think I was proposing that they go into an uncharted forrest (something I did as a kid).
I even remember seeing a bus stop for the middle school directly across the street from the middle school (can not find the link to my post about that). Note: The street in question was not a major highway or even a particularly busy street... certainly nothing that should be a problem for any 10-14 year old to cross.
But just to clear things up, it should be noted that it has never been safer to be a kid in America.
There just is no reasonable reason to not let kids run around and play. They are not in danger and never were.
Got this post via boingboing that helps illustrate some of the problems I see with anti-Free Range people: Middle school principal's (non) helpful email to parents about social media
The author analyses a letter he got from his kid's principal expressing fear of Instagram and expressing an urge to protect the kids from nasty comments. Our children grow up so fast. Let them stay young as long as we can.
Wrapping your kids in bubble wrap helps no one and only exacerbates the problem. Let them out and let them get hurt, then let them know that when they get hurt, you will always be there to help them back up so they can go out and try again.
Sure they will never get hurt if they never go outside, but they will also never learn how to handle the little hurts and troubles that the world constantly throws at them.