I once asked a friend, during a nosy discussion of our respective sex lives, under what conditions he tends to most enjoy sex. I figured he might talk about particular sex acts, positions, or roles – but instead, he said: he strongly prefers sex where everyone involved is completely naked. He'd had awkward experiences before where this was not the case, and so now he felt most relaxed, most free, and most receptive to pleasure when he and his partner both disrobed completely beforehand.
I must admit I was surprised by this, because nudity has never been a particularly important aspect of sex for me. A lot of times when I masturbate or have sex, I only remove the articles of clothing that are directly blocking my path to the relevant bits, and sometimes not even those – a wand vibrator works perfectly well through pants and underwear, after all. If a higher proportion of clothes come off, it tends to be because the person I'm fucking initiates the removal of clothing – or because I'm overheated and need to cool down.
I just don't really care about being naked, and sometimes it's actually sexier if I'm not. Maybe my positive associations with half-clothed sex come from the days when, as a teenager, I'd keep my outfit partly on during sex in case a family member were to open my bedroom door (which lacked a lock). It almost never happened, but each time it did, I was beyond grateful to be able to flip my skirt down and instantly conceal any evidence of tomfoolery (besides maybe my blushing face).
I think a common reason people may not want to get naked during sex is some flavor of body image issues, whether they be dysmorphia, dysphoria, or just the toxic soup of self-judgment we're all fed all the time by tabloid articles and social media. This mostly isn't a factor for me currently, because I know and trust that my spouse adores my body, but it has sometimes come up for me in the past, especially when sleeping with newer or short-lived partners who had not yet expressed liking how my body looks. I want to be able to relax and enjoy myself during sex, and sometimes it's easier to do that if I keep my dress on, so I don't have to wonder what this new person thinks about my stomach or boobs.
All of that being said, I think the hottest thing (for me) about clothed or semi-clothed sex is that it conveys a certain urgency. Some of my most-replayed sexual memories are the ones where a partner was in such a desperate hurry to get their mouth on me, or their dick inside me, or whatever, that they couldn't be bothered to take my clothes off before diving right in. There's a cinematicness to this type of sex, a dramatic flair, a demonstrable sense of desire that really appeals to me.
One other key reason some people like clothed sex is that clothing itself can be exciting, in a fetishistic way. Noted kink educator, and fetishist of latex/ rubber/military uniforms/gas masks/leather boot/etc., Danarama, has a line on his FetLife profile that reads, "If we play, you would best not be naked," and I think of this line whenever I think of wearing lingerie or leather or pearls or heels during sex. I'm not into these things enough on their own that they stir up intrinsic desire for me, but they can make me feel hot and cute, which can help a lot with sexual confidence.
I got the idea for this piece because I recently wrote a fully-clothed sex scene into one of my fanfic stories, and realized just how many of these I have written over the years. But I also recently had a sexual fantasy along these lines, the kind that comes up unbidden when you're horny and teaches you new things about your own sexual psyche. In the fantasy, I went out for drinks with a crush, and then invited him back to my apartment. We were making out in my bed, fully clothed, and he pushed one of his thighs between my legs to grind it against my cunt while we kissed. The pressure was getting more and more intense as our kisses escalated, until finally I somehow had an orgasm against his leg. "Wow," I panted; "That's never happened to me before!” He grinned wolfishly at me and said, "Really?!"
It's telling that this fantasy turned me on & that I got off to it. I think it speaks to the hotness of that urgency I mentioned earlier, but also something that's harder to describe: the thrilling tension of knowing that although sex is a traditionally naked activity, our bodies can be fickle and unpredictable, and can experience pleasure (or even orgasm) without any clothes needing to come off at all. There's something terrifyingly intimate about the idea that someone could make me come through my clothes – that my body and its responses could be that embarrassingly available to someone, without me even having to allow that vulnerability by stripping down first.
I suppose this is also why I sometimes fantasize about being the top in that scenario – making someone come in their pants without having to take any of their clothes off, or maybe without even touching them. Arousal and orgasms are these achingly personal bodily responses, and we try to hide them behind our clothes, contain them neatly inside our underwear, until we're ready to let them loose. But if someone can make you come without removing so much as a single layer, well... they might as well be able to see into your soul, and I think that's pretty fucking hot.