It might be to protect Sinister's image.
Sinister's thing is being the supergenious, so when you put him with another supergenious thats not at all impressed that might be a bad look for him.
There is an instance where Banner, Reid, and all the smart heroes are trying to stop something cataclysmic from happening so one of them is like we need more brainpower and they teleport in Dr Doom, Dr Octopus, the Leader, Wizard, and like a bunch of smart villains all at once cause its bigger than good/evil they are tryna save the world... but Doom and DocOct and Reid and the
really smart people start brainstorming and everytime the other lesser smart people like Peter Parker or Trapster or somebody tries and add an idea Doom tells them to STFU actual smart people are talking.
So you got Wizard and all the B villains and heros who are normally looked at as brains looking like bytches cause Doom wont even let them talk.
(Then of course a fight breaks out)