So, I don't know too much about the competitive scene of Smash 4, but I was wondering: What stages are considered "legal" and why are others banned or not played?

To my knowledge, Town and City, Smashville, Delfino Plaza, FD, and Battlefield are the stages that are mainly picked in the tournament videos that I've watched. Why aren't others picked, like Omega versions of stages, or any of them with stage hazards like Bridge of Eldin or Gamer?

I understand for the walk-off stages, like Coliseum, it'd be pretty boring to watch players just throw each other off the screen and abuse that. I can also see why Palutena's Temple and GCO would be banned since they're massive.