The reason? Unified rules. No more soccer kicks to downed opponents.
Personally I'm fine with that. I'd like to see knees allowed against downed opponents, but I've always found the stomps and soccer kicks brutish and barbaric.
Now I may not like soccer kicks but that doesn't mean I don't respect and admire the awesome Chute Boxe team. They're the best proponents of Muy Thai in MMA. Ironic since they're from Brazil. Their feuds with the Brazilian Top Team, Takada Dojo, Hammer House and others have been all time greats.
My favorite Chute Boxe fighters, Jose "Pele" Landi-Jons, and UFC middleweight champ Anderson Silva left the team a few years back under a weird cloud a few years ago. Something about racism, but I never got a clear understanding of it.