And what's particularly frustrating is that many organizers will try to combat this by writing papers saying they "particularly encourage" papers that are interdisciplinary, or focused on less fashionable topics, etc. It's good that they are trying to change things, but I think the main effect in practice is to encourage people to spend their time writing papers that have little chance of being accepted.
This issue isn't at all unique to computer science, though. Try publishing a paper in a top economics journal as an outsider!