If kids are living in a world where every little thing they do is checked out for safety, then they will assume that nothing can harm them. There are too many crimes and other things being committed. Children need a wake-up call. Their wake-up call is getting bumped on the head from a slide or skinning their knee from jumping from a swing high in the sky. If we just concentrate on the little things in life and put the larger problems off to the side, then we will have big problems for the future.
All parents worry about are themselves.
They have never stopped to think if their child bumping their heads would teach them a lesson. Just like a woman said, one day her little toddler son walked by an open oven and touched it. He then burned his hand on it. The next day his mother told him to touch the hot oven, and he did it and got burned. To this very day he never touched the oven again unless he wore mitts.