This probably isn't as legitimate, but if someone doesn't like a site that changes frequently, they probably won't like it. It's been a while since I've been to hacker news, but it seems pretty static in that the features don't really evolve, just the content and discussion topics. Whereas stacker news is constantly evolving, improving, etc. For some, that may not be as comfortable.

Yes, this is a "my greatest weakness is actually a strength" argument, but I do think for some it could be unsettling.