As a freshman in college, I feel I am 'supposed to like' beer and parties. I don't. I like Cuba Libres, and relaxing in the dorm with floor-mates, but that's beside the point. As an avid reader, I feel I am 'supposed to like' the accepted classics of literature (Mrs. Dalloway, Ulysses, etc.), but I don't. I generally consume pulp fantasy and thrillers, despite being perfectly capable of reading said classics. I liked the Great Gatsby, Les Miserables, and Dracula, but that's beside the point.

In my opinion, when you feel you're supposed to like something, it's because a group of people with whom you strongly identify (lovers of Beethoven's music) like that thing, and you've adopted that group as a sort of label for yourself. It's easier to say "I am an aficionado of classical music" than "I like classical music of many types, in particular Canons, I love Chopin's nocturnes, I appreciate..." and thus one gets the feeling of "My feelings should more closely tie in with those my label would indicate."

We sometimes see the same thing with political parties.