The point is ... he is a "Houself" so he is treated badly .. and with no respect like cockroaches and everything.
But!!! in the Book and movies .. he is like one of the best magicans. He can cast WITHOUT a wand ... and he doesn't need to say the spell (in the movie I am not absolutly sure about the Book atm.)
So he is a better magician than his "master"... but why ?
That is what I always wondered about .. because in a magic world .. the better skills should lead to a higher ranking and reputition .. but houseelves are like slaves.
Did anyone ever thought the same Stuff ?? ^^