I'm not sure why the city/catholic league doesn't have a senior all star game, the league organizers would have to answer that. I would guess that Monroe County has a Senior game because the players in Monroe County don't have the opportunity to go on in their season and play in sectionals, regionals or states. The Senior game gives them one more opportunity to play.
This year will the first in about 5 that the Private-Parochial league will have an All-League team. It took that long to get all of the AD's to agree to that (and chip in a few bucks for trophies etc.). I don't think that the City League has an All-League team either. So that's probably the first hurdle.
As for the Senior All-Star games, there are rules that need to be followed. I know it took the Monroe County League 3 or 4 years before we finally had a All-Star game.
There is a form on the Section V website to apply for an All-Star game, and there is probably a set of rules some place. I just haven't found them yet.