Here's my guess ...Right now, some teams have to travel across the country twice in a couple of months (this year Arizona and Texas) and it looks like the new winter format makes it 1 event to qualify for the nationals -- which reduce the cost on clubs and families for all the travel.
Admittedly, USYS pathways to the national championships are super confusing and seem aimed at giving clubs plenty of chances to qualify. You can qualify through these winter events, mostly teams from Elite 64 OR you can still win your state cup/do well in the National League and qualify through that competition.
And they also have something called Presidents Cup -- another national tournament for winners of the second-tier division of the state cup competitions.