I agree with most of your post, until the "why" question at the end. There is no Why?, it's very simple. It's not about the players, parents, or coaches. It's about tournament directors and $$$. 10am start means fewer games over the weekend, which means fewer teams in the event, which means fewer tourney fees.

Yes, more and more complexes have lights, but often there are permitting/zoning issues with having them on late. My town it's 11pm, and I've been told by park district people that the phone calls start at 11:01, if the lights are still on.