This isn't just "PS3 People Kerfuffle", this is uniting characters from all parts of Playstation. People loved their games back in the day, the nostalgia boost would make people who loved those games back in the day feel remembered. Besides, Superbot is aware they are, at this point, the characters we all want in, so they would try to get them at the very least. There's a lot of fans who want them in, and upsetting them isn't a good thing.
All-Stars Conquistador Music Video: https://www.youtube.com/watch?feature=player_detailpage&v=fJp-EtS0QQk