I believe that in the modern world anyone willing to be a referee is probably running a system they like. There are always exceptions and locations and circumstances where it is hard to organise a game.I'm not ranting. But D&D is by far the most popular RPG. You think everyone playing 5.5 is doing so because it's their favorite RPG and they wouldn't play any other game or version if it was entirely up to them? People on this forum have said otherwise. People play the games they do for all sorts of reasons.
For players the matter is not as clearcut, but to be honest, it they are not willing to run a game I have less sympathy for their plight.
It may be less true for some online games but in my experience, players will go along with the referee's preference, particularly younger players (especially if they do not have to buy the rules). Once players are facing 60 plus, they may be less willing to learn a new set of rules.