JusticeItEasy said: Plus they are pathetic, tasteless, talentless and delusional villains, even The Joker, Sephiroth, etc. have some standars to avoid such villains that would make them look bad.
It's like if they teamed up with some lame ass Soap Opera "villain" or Barney Kid show tier villain. It would ruin their image.
Or maybe... They don't know who gathered them together...