Right, exactly. But its the interactions between the characters who have never met onscreen that is less interesting to me. I'm not saying I never read crossovers -- I do, and I've written one ficlet that is a crossover, and I really enjoyed some of the Into A Bar ficlets I read.

But that's my impression.

Fandom loves them, though. They have only grown in popularity in the ten years I've been reading fanfic, it's my impression.