great question
in my view, in a state as large as texas, for example, there are a lot of kids who live in smaller markets, and to play on a top level summer teams means a lot of money and separation from family, etc at a pretty young age. for that matter, i suspect that some of those in the smaller, rural markets don't even know about some of the top summer leages.
in far west texas, for example, most summer play is on school-based summer teams, and those who travel off to play in the summers are viewed as disloyal by those coaches and parents who don't know any better. puts a kid in a real awkward situation - do i stay on my school summer team and play in obsurity all summer, or do i spend the summer away? although it violates every rule in the book i know of kids who have gone off for summer ball [and future d-1 careers as a result] but who lost their h.s. position as punishment for not staying on the school summer team. more than you wanted to know, but that's what i see in different parts of my state, especially outside the larger metro areas.