Why is Spider-Man excluded from The Avengers, X-Men, and FF?

[Darthfury78]

I think that Spider-Man would do so much better(sales) if Marvel avoids repeating the same past stories. When was the last time Spidey encountered The Morlocks? All I see is segregation among Marvel's editorial departments instead of partnering up and exchanging characters and story ideas that might do better respectively. Marvel is a business. Yet, they don't treat it like one. If they want their books to sell as much as the Japanese Manga, they need to upgrade their business model as it's been stuck in the past since the early 1990's. What would be an improvement is to make Spider-Man a member of The Mighty Avengers, which Marvel hasn't done since Bendis left the series. Segregation equals a loss of opportunities to make the readers buy the product. I never understood why Spider-Man is excluded from The Avengers, Fantastic Four, and The X-Men. Peter would fit in well with either of them as he would bring his fanbase with him. Kaine Parker would fit in well with X-Force.