In years past it was for all high school age players. There are some rules that involve having to have a few guys on the team from another school in order to skirt some VHSL restriction. Same reason why varsity coaches don't run it.
Unfortunately it has tended to be very low quality play and as a result, the organization of it has struggled year to year. Between the guys playing football and the guys playing travel, it's sometimes hard to find 9 to play week to week.
No idea what's going on this year or even if it is still going on. My two cents is, if you miss it, you didn't miss much.