I bowled in a non-sanctioned sport league a few years ago. I believe it was still USBC sanctioned, though. It was more money to sanction the sport league on top of the regular fees. I personally believe in this instance it really worked out for the league. Sure, no one was going to get a special sport bowling ring for shooting a 300 or 800, but the chance was pretty slim for the group of bowlers.
As far as non-sanctioned leagues, I have no problem with this either. They come up with their own set of rules and everyone is on board. You shoot a 300, well, then you don't get a USBC ring. If the league provides another award, fine, but that has to be spelled up front. If you think about many of the USBC rules, some of them still refer to league rules for guidance.
I just don't think the USBC and local associations are doing enough to make sure at the center level that centers, leagues, and tournaments are up to the rules.
Dj