From about the age of 4-5 my brother (now in his 50s) played outside with his friends for most of the evenings, and all day on the weekends and in the holidays.
I am in my 40s, I was an uber nerd kid, but even I played outside , with other kids, without adult supervision for hours at a time on a regular basis.
My kids only get this experience when we go camping.
Kids need to be with other kids without an adult breating down their neck all the time. It is when they get to do all the annoying stuff that pisses off the adults.
They need to do it, and we need to let them. Not only for their good, but because it helps us if we give them feedom in little doses.
Jimjams has mentioned in the past children who are growing up to think that the world revolves around them. these are the kids who are mollycoddled from morn to night, with constant praise and support and encouragement. It isn't good for them. Played with, entertained and shipped from one structured activity to the next. Kids need to get the corners knocked off them by other kids. They need to learn how to entertain themselves, how to deal with boredom, how to deal with other kids that they don't get on with.
I'm not advocating neglect, praise is a wonderful thing, but not all the time. And guess what, we end up far less stressed, with less navel gazing about the relative benefits of water and juice, karate or judo, ORT or 360 Ginns.
We all need to take a chill pill and let the kids be kids.