I´ll think because Rainbow have to be banned. Is similar to Jungle Japes, is autowin.
For me, if Rainbow Cruise was banned, I'd have no problem with Jungle Japes being banned. But if Rainbow was allowed, there would be no reason for Jungle Japes to be excluded at all. Both stages have the common trait of only being
VERY beneficial to a handful of characters (MK/GaW in RC and Falco/DK/Peach in JJ). It's unfair how Meta Knight, who already has so many advantages in this game, gets a true shot at yet another huge advantage: having a LEGION of stages at his disposal. As I said before, Rainbow Cruise will most likely be banned against the MK player, and so it becomes a dummy stage which allows the MK player to simply pick Brinstar, Delfino, and countless others.
MK stage quality
********: Rainbow Cruise
Excellent: Brinstar, Delfino
Great: Battlefield, Frigate Orpheon
Good: count them if you want... >_>
As you can see, if you exclude RC from tournies, people will at least have the choice to ban either Brinstar or Delfino. And that would be good really, considering strong aerial characters like Wario and R.O.B will most likely ban Delfino because they're better on Brinstar, and ground based characters will prefer banning Brinstar.
Please consider this, guys...