Because it is very frustrating to say "I like [thing!]" and then automatically be categorized into a group of people that you don't like or even necessarily agree with.
If I say, for instance, that I like Rush, I don't want to be categorized with the same group of people who eat, breathe, sleep, fart and fuck to Rush, know every song by heart, and can tell you the most inane details about everything about Rush ever. These people exist. There are far more of these people than there is any right to be, and these people actually repel me from enjoying Rush in any capacity because I link Rush to them and it's a gross connection. I like Rush. They will go on their knees to suck on Neil Peart.
I'm sorry, I'm tired and a little ranty after listening to my ex explain to me (again) how Neil Peart is the best drummer ever. But I hope it explains my point.
Also, furries.