The One Question That Consistently Nags At Me

Why is it that some people feel a need to judge other people for their personal preferences and/or their choice of recreational activities?

To me, this ties in very strongly with the whole concept of the "harm principle". If one's person's choices are not... by any way, shape, or form... causing harm to other people - then why do some people feel a need to belittle or mock someone for, essentially, enjoying things that give them pleasure? Why should people be judged for, essentially, deriving happiness or pleasure from certain things?

Like music, for instance. The only time I can really understand being judgemental of one's musical choices is if they are making the choice to play their music at an unreasonably loud volume that it's bothersome to their neighbours. Aside from that, I don't get why some people feel a need to judge other people by what music brings them pleasure. Do you get what I mean?