Player limitation mostly, depends on what videos you're talking about though.
Failure to grab Marth can be punished pretty heavily. Dunno why someone wouldn't try to chaingrab MK though, that's easy. You have to be frame perfect with the air-release chain grab on Wario if he still has his double jump, and if you miss there is the chance he can chaingrab you with his dthrow, but it's not guaranteed or anything.
Failure to grab Marth can be punished pretty heavily. Dunno why someone wouldn't try to chaingrab MK though, that's easy. You have to be frame perfect with the air-release chain grab on Wario if he still has his double jump, and if you miss there is the chance he can chaingrab you with his dthrow, but it's not guaranteed or anything.