People who complain about the "singing for no reason" thing are bonkers
It's a little unfair to call them 'bonkers'. Granted it isn't particularly nice or encouraging to complain, but many people quite reasonable often have legitimate (if unusual) reasons for their preferences.
It's like complaining about robots and aliens in science fiction.
It's exactly like that.
Some people like plays but don't like Opera for the same reason. Why ruin a perfectly good play with an orchestra, arias, duets and what have you? Similarly some people don't like dancing or even just watching 'purposeless jumping about', or maybe ballet because 'it's for girls'. Some people don't like sports or even sport films, because they never played them and could never get interested or see the appeal. Others don't like mysteries, like say Agatha Christie because 'it's silly having so many needlessly complex melodramatic murders in quiet English villages'. Similarly classic noir isn't to everyones taste because, 'it's too old fashioned', or animation and anime 'is so childish and immature', or because science fiction is 'technological wish fulfillment for boys', or fantasy's 'not good serious adult drama', and so on. War films are too violent, comedies crude and so on.
Preferences as effective filters are necessary for maybe at least two reasons.
Quality: there's just too much stuff (most of it garbage), simply too many shows, books, films, magazines, web sites etc, for any but an immortal to claim encyclopedic knowledge, or experience any significant fraction. You have to have some sort of heuristic to deal with the mounds of possible things that can occupy people, and preferences are a way of winnowing down an unmanageable heap of mostly uninteresting things.
Quantity. Almost ironically, once you've refined your preferences, into what might be called a good aesthetic sense, you being to winnow out the chaff, with your discriminating choise, and you're theoretically left with a lot more quality stuff.
Of course where people acquire their preferences (early exposure, imitation, availability, affinity, etc) and how they naturally develop and change are a bit mysterious and probably idiosyncratic, and there's tension between the uncertain risks of new experiences and the law of diminishing returns, but some sort of system of preferences as filters is probably necessary and desirable.
As a final tangent but related observation, art and media sort of go in short (fads) and long phases. Stuff like Waltzes probably had their heyday at the turn of last century, similarly some arts/sports/crafts are no longer as prestigious as they once were, or slowly declining (maybe Ballet, embroidery, Polo, or dressage etc), while others are new or increasingly vital (youtubing?, video game design, video criticism, geotagging etc), obviously related to developments in technology. In some respects, the heyday for Musicals maybe has been over since it became easy to record music off the radio, and certainly after music videos. Video killed the radio star...
Sorry to go off on you, 'bonkers' was triggering ;)