Couple things:
1. During the rites, the ragers don't all bust out of the village and start killing people. They sit there and kill each other.
2. The rights aren't a big excuse for people to go all "Stevers" in-game and act retarded.
3. OrcFest's entertainment factor is primarily extra-game. That is to say, people enjoy (on the forums, etc.) the idea of all these retarded orcs running around. The rites are coordinated (in game) using an ooc reference to time, but that's by necessity not design.
Consider if Tremblefist had sent out an IC note urging the Grinning Skull women to reproduce as many new offspring as possible. Basically and IC version of OrcFest without all the QHCF exposure. Somehow I don't think you'd have as many people rolling up orcs.