The best thing about PGF is that it provides another opportunity for players to be seen by coaches, the better because it's in tournament format.
The second best thing, if you're from SoCal, is that it's dirt cheap.
Those two things alone account for it's popularity with CA teams, invited or not, hence so many teams playing in the SoCal qualifier. But with only 4 berths available in HS division, (there are 5 times as many invited teams as there are berths available to SoCal teams ) many teams won't be going to any nationals, leaving a lot of disappointed players and angry dads.
The net effect being that next year many SoCal teams will be looking at alternatives, because players just want to compete. The players also know that some of the invited teams wouldn't stand much of a chance of qualifying this weekend, and that whole cronyism aspect of the tournament isn't going over very well in the general softball community.