Lisp culture contains the attitude that this is the right way to do things, and other ways are worse, and choosing them is a mistake. Thus, for anyone to take up Lisp, they have to admit to themselves their past decisions were mistakes. It's a lot easier to say "screw you, I'm right" and not switch over. If Lisp is right, they wasted a lot of time and effort, so they are invested in it being wrong.

The same thing happens in other fields.