I can totally understand why there is/was a fic-writing fandom as well as a more general and enduring Beatles fandom - the 'narrative' of their lives is fascinating, and the emotional connections and difficulties are so dramatic.

I can also understand why Paul's songs would be more likely to be covered than John's—they're more accessible and less 'sharp', maybe. But that's a very sweeping and general statement. They just had that amazing chemistry that generates greatness.