Their copyright, of course.

Superheroes are cool. And make them owners make money. Lots of money.

The need to milk this cow is so big that it had to be saved “from the crushing weight of its own data” with at least one massive database.

Yes, that huge ball of white and blue spaghetti is a graphical representation of the links in that database.

In spite of that, thanks to the madness and idiocies of current copyright, you will never, to just make one of many examples, see the X-Men and the Avengers sharing a screen.

The reason is that the owners of all the future movies, graphic novels etc… on not just superheroes, but every other “pop legend” of today, from Luke Skywalker to Captain Kirk are a small, awfully interlocked mix of competing corporations.

Of course, this is true in every branch of culture. Comics just are a simple way to realize how bad things are. To understand it even better, have a look at these slides of mine about creativity in comics vs modern copyright.