We move from ruffle-butt to panties, starting with character panties then "fun" patterns. When I was a kid, I had the typical "Days of the Week" underwear. I hated it. I never wore it on the right day, and I lived in paranoia someone would see it: they’d think I’d been wearing my Tuesday underwear all the way until Friday. But other than that, I didn’t notice my undies. Pre-pubescent girls don’t.
In high school, we break into Victoria’s Secret. We start with the silk and lace, but by the time we’re driving to our boyfriend’s house, we’ve moved up to the thong. The thong: an utterly impractical garment, whose crotch is never large enough to cover everything, and which requires trimming to wear properly.
Once you’ve moved up to thongs, you’ve moved up to pubic shaving, that rite of passage that seems so grown-up beforehand and so miserable in retrospect, fraught with ingrown hairs and sharp stubble. You have to mean it to wear a thong – you are a sexual being, and you’ve not only accepted that, but celebrate it. All that silk and lace was just practice for this. You’re going to get laid for real now.
The thong also means you’ve crossed the border between wearing underwear for yourself, and wearing underwear for someone else. That someone else might be other girls, who see the edges of your thong peek out from your jeans and realize you’re daring enough to wear one. Or it may be boys in general, who you hope will see what we used to call a "whale tail": the back of your thong rising up over low-cut jeans. But it may be for your boyfriend, who you want to see it, but not see it.
Once you get to college, you’re still wearing thongs, but with silk and lace to balance it out; you claim thongs are “comfortable.” This is a lie. Thongs are only comfortable once you get used to something stuck up between your butt cheeks in a perpetual wedgie.
Eventually you stop caring and your careful bra-and-panty sets fall by the wayside; you meet someone. You might put on the lace and silk, the thong, or the bra and underwear for them, but eventually, you’ll revert to normal undies; basic cotton panties. Your significant other will claim, like Elvis, a fetish with white cotton panties. He’s grown up, too. He cares a lot more about the present than the packaging.
Then you move into maternity panties. Maybe you don’t buy the ones explicitly for pregnant women, but you buy cotton ones a size larger than you’re used to. And you have to buy plenty of them, because between the sweat and the pregnancy discharge, you’re running through two pair a day (at least). Alterntely, you start wearing pantyliners like a middle schooler.
Next, you have your baby, and you have the shortest, but perhaps the most memorable of all your underwear experiences: the mesh panties. The mesh panties absorb all the stuff coming out of you, and hold an ice pack to your poor, bruised, and perhaps torn girl parts. These things are awesome. You should stock up on them in the hospital and demand more. But really, you’ll be rushed to get back in your own panties as soon as possible, and you’ll leave that wonderful mesh behind after a day or so. You won’t make this mistake with subsequent babies.
Then you’re back in maternity undies. You swore you wouldn’t be that person wearing them postpartum, but you were wrong, wrong, wrong. Your butt’s still big. Your stomach’s got a sag. You need those maternity undies for adequate coverage (and pad holding).
But eventually, you’ll be back in your pre-baby cotton panties, which you’ll wear because they’re no-fuss, no-bother. You have children. You don’t have time to think about underwear. And sex? He’s lucky he’s getting it. Your chances are so few and far between that you can’t predict it with fancy underwear.
Until you start caring again. A time will come when cotton panties won’t do it anymore. You'll want to get back to the silk and the lace, and maybe a thong or two. You’re accepting yourself as a sexual being again. Despite having a baby, you’re still entitled to look sexy, to be sexy, to have sex. The quickie might come back. Your significant other will appreciate this. They’ll be glad you’ve come back to caring. But you won’t be changing for him. You’re wearing this stuff for yourself. And that’s the best reason of all.