Umpires turn games in for many reasons. Quality may be one reason but who your partner is can be a big one. I've know some guys that nobody wants to work with. I think the best reason is work related. The end result is turning games in drives assignors nuts.
For the guys that are turning bad games in, when it comes time for the good end of the year games guess who gets first dibs. The guys that didn't turn games in and the guys who took the turned in games.
JV games should pay as well as Varsity games because they are harder work but in the real world there just isn't the money.