I don't actually care about those things, but many of the people I know do; And because of that, I make a very deliberate effort to keep track of them. A new perfume, a dress I haven't seen before, a different hairstyle - noticing these things and acknowledging them in conversation is part of being polite and maintaining friendships.
I came late to it though; I did not pick up on many socialization clues "naturally" the way a lot of people did, and a lot of "Normal" emotional buttons just don't seem to be hooked up to anything for me. On the other hand I did not learn to ignore socialization clues "naturally" the way many people did either; I struggled with them for years.
I learned things, one at a time, in many cases years too late. I had no idea for example that there was an expectation to call someone the day after a date, until once for some unrelated reason (schedule of something the following week) I happened to and she said she'd been "afraid you weren't going to call...." and after my brain cranked that one through I realized at least one of the things I'd been doing wrong and one of the reasons I'd been a social failure. I also had no idea that people were expected to hate their exes, or hate their exes' new romantic partners, or even that some kinds of romantic relationships were considered "normal" and others weren't, until after I'd been doing things, sometimes for years, that ran contrary to the "normal" expectations. I never got the thrill of "Transgressive" behavior for example; for me it was an empty category.
On the one hand I was utterly oblivious to what apparently is obvious to most normal people socially from clues I never noticed; on the other I was always observing and trying to learn to do better. (Gender roles: HOO BOY gender roles. I never even frickin' NOTICED that there WERE gender roles until I heard people talking about whether or not they felt suited for them. I'd noticed sometimes that people called one thing or another that I did typical of one gender or the other, but that was mostly irrelevant; they were the things that I did because I did them, not because of any gender thing. The idea that somebody's idea of what "male" or "female" was supposed to be, could be a really important contradiction to their own idea of who THEY were supposed to be, was a mind-blower for me).
But anyway, the short version. It's that paying attention thing. The process of picking up basic socialization well after I was supposed to, requires constant attention to individual people. But among other things, paying attention to individual people, all by itself, is one of the most important parts - maybe the MOST important part - of social behavior.