We have carnival queens and princesses where we live. Every year there are fewer entrants, but that goes with the general dropping of involvement of 'community' and correlates with fewer carnival floats etc.
I know quite a few girls who have been princesses, and it isn't a 'beauty' thing, it is about representing the town at other carnivals, and representing the carnival at other events. e.g. One did a welcome at the Christmas lights switch on. They have all really enjoyed their year of princessing.
I think it is nice to open this up to boys too.