Not a dancer myself, but I’d venture a guess that the kind of person who dances a lot’s main goal is not to look smart, but to have fun and/or employ a time tested and outrageously effective means of attracting sexual partners.
Exactly this. It probably varies from person to person, but tapping my foot when listening to music at a computer in rythm with the song, or just noding my head slightly makes me way more invested into the song. Doing anything in sync with music is satisfying - that's why games such as Beatsaber or BPM - Bullets Per Minute are sooo satisfying to play - if you don't get dancing, I recommend giving BPM a try.
And dancing is basically the same. You don't do that for others, but to enjoy the music more. And especially with drugs or alcohol involved (because it usually erases any kind of self-consciousness and focus on how you look, so you can focus just on the music), it just feels so great.
And as for ballroom dancing - being so well in sync with someone in addition to the music is an amazing experience. It takes time and requires a stable dancing partner, but once you eventually sync with eachother and know the steps well enough that you don't have to think about it and it just flows, it's an experience unlike anything I've had with a second person. And my dancing partner isn't even my girlfriend, but just a friend.
One comparison I can make is what I had during highschool, where I've wasted several years literally only playing League of Legends with my best friend for all of my free time. We played ADC/Support, and after few hundreds of hours we were so synchronized that we would could instinctively react to each other without thinking or talking about it, and it was a really weird experience. And really interesting, I've never experienced something like that with anyone else (before I started dancing, that is), and it's such an unique connection of minds and thinking that it's an amazing experience.
this is something that has always bothered me... I never found the appeal in that and, of course, was pressured by social circles to join in on clubs and similar. this just feels like the most stupid waste of time, as I can't find any enjoyment on it, and when I watch others doing it they surely look weird and lost in a way. specially the ones I know personally and can attest to their intellect and rational.
eventually I stopped joining them but it kept intriguing me. after reading about it and having long conversations with friends, my conclusion is that this is some left over form of primitive sexual bonding that predates complex speech and became instinctual, a la some "mating dance" ritual. particularly, some more enlightened male friends see that as a "necessary evil" to have sex while others simply never gave me a clear answer (probably don't ask themselves much and just abide by the social rules). the only thing I could pull from females has been a dismissing "I just like to dance".
so much so that I could (anecdotally at least) observe very repeatable patterns such as: single couple that eventually meets in a party then stops going, girl that simultaneously loses interest in their partner and gains interest in clubbing which ends up in "someone new" popping up, etc.
as for myself, I can't really explain the lack of drive. I know for sure I'd rather communicate using actual language and not be in crowded, dark places moving my body aimlessly, faking enjoyment. needless to say, this stance heavily lowers one's chance to mate, as the whole paradigm revolves around it (at least outside of the dreadful online dating world). so sometimes it can take years for me to develop a new relationship after one has ended. fun fact is that every single one of my girlfriends loved to dance, some even took classes on artistic styles and whatnot.