I'm not a parent, but I can imagine how difficult it must be for some parents to be able to "let go" in this way sometimes and let kids be kids.

I think if I had kids my gut feeling would be to prevent harm and unpleasant experiences, because I wouldn't want to experience those things myself, much less those in my charge who may not be equipped to handle it as well. If I allow myself to be driven by that instinct however, they'll never be well equipped which does not make for a well rounded adult. It hurts to see immediate family hurting even in trivial capacities, but a parent must seemingly be able to endure that if the children are to come to be able to stand on their own.