There is Quidditch in the fifth book, but it is overall unnecessary to the overall plot, it just would've been nice for them to put it in.
Prefects (the thing that escapes you) haven't really been mentioned in the movies. I think Percy mentions that he's one a few times during the films, but other than that they aren't mentioned or explained.
It'd end up being a concept that'd needed explaining and slow down the overall pace of the movie.
But I am hoping that they show some quidditch in the 6th movie seeing as the only really important plot points that need to be in the movie are the memories and teenage love.
Bullet Tooth Tony: You should never underestimate the predictability of stupidity.
Reporter on Titan Maximum: Sasha is there any connection between your poor album sales and the fact that it sucked?