1) Authentic music appreciation. Look, Britney Spears can't possibly enjoy performing "Baby One More Time" anymore, because she's sung that one a trillion one more times in her life. I believe she no longer feels the same way about it. But the person who karaokes "Baby One More Time," perhaps, still genuinely loves that song. They've performed it nonce or only a few times, so it still has the chance to feel fresh. The song is precious to them and they want to be a part of the song.
2) Karaoke is a wonderful art form for our smart-phony selfietastic culture. The gadget-fueled Interweb is constantly saying it's all about you, you, you, your personal preferences, your customized experience. Live concerts are inundated with people taking videos and photos to preserve the moment, to prove they were there. What better customized experience than a show where you are the show?
3) Diversity. Because there's a subgroup within every group that really likes karaoke (and because it's a niche activity that is not even as hipster-cool as, strangely, lip-syncing), the crowd at a karaoke bar ends up being more ethnically diverse than a bar which caters to a certain age, race, or sports affiliation.
4) Everyone who karaokes is demonstrably more beautiful in the karaoke room/bar than in normal life, because when you sing your face is open, which is not always the case in daily activity. But when you sing, you can't help it.
5) I have a youtube channel about this stuff, btw, at karaokerhapsody.com.
7) Music is a far-reaching force which constantly reminds us that you do not have to be skilled at making music but you may still passionately love music. It's an imperfect world.
8) It makes you feel better about your day. I'm pretty sure karaoke will eventually be approved as an effective therapy for any number of psychiatric conditions. You can get addicted to it, too.
9) Karaoke is a distinctly Japanese import, and is one of those funny loan words to English which originates in a loan word from English: the "-oke" is short for "okesutora," a Japanese version of the word "orchestra." (The "kara-," also used in "karate," is a word indicating open, empty, or space.) So it's got some East-West fusion history, and of course is a social staple in the Asian American community. Whether you pronounce it in the English conventional usage way (Care-Ee-OH-Kee) or the Japanese-correct way (more like "Kah-Ra-Oh-Kay" — Japanese has the same regular vowels as Spanish, peoples!) doesn't reallllllly matter, but is sometimes a good indicator of how hip to Asian culture the speaker is/thinks they are.
10) Every human has had at least one perfect moment in their life; I think there's some sort of statistics principle to argue for this, given that a) the moment is not necessarily very long b) people's ideas of perfection are totally subjective and individual. Your perfect-est moment is the comparison basis for all other good and bad events in your life. Everyone spends a lot of time trying to sustain or reclaim such moments. In my observation, a perfect magical moment happens at least once in every karaoke night. It is easily missed, and may be right adjacent to an awful moment within the same song. In most bars, people basically are chasing the same three goals repetitively, and a "typical" evening might pass without event or embarrassment, but also without anyone knowing a magic moment in the course of trying to get drunk, laid, or loved. In karaoke culture, there is that one indivisible moment, at some point, every night. That's the one that I'm looking out for, as a participant and an observer. Even when it is not fun or good or exceptional, karaoke aids us in squeezing emotional content out of our time on this rock.