The way I see it, the overly non-subtle style of dialogue is literally just appealing to the Western porn market. Dialogue in professionally produced Western porn is the same thing, pretty much, with women referring to themselves and each other as wet, horny, cum-hungry sluts desperate for a little bit of Fuck Time. That's probably why games like Phantasma and Harem Heroes and Pussy Saga can't go more than 2 lines of dialogue without sex coming up in some way, because the goal of Western porn is to get roiiiiiiiight into the puss. It's not about world building or character development, it's about making a man's pee-pee go into a woman's no-no place, or the collective phalluses of 5 men encroaching upon and exploring the myriad orifices of a single woman, or... Lesbians, but pretend I said it in a funny way like the previous two things.

If it's not direct appeal to the market, then it's just the devs being influenced by the market in the same way that they're influenced by the games they rip off and the art they trace: Expend as little effort as possible to make a game that people will play and pay for. The PS devs didn't need to think of a game idea because HuniePop exists, they didn't need to create original art because other art exists, and they certainly didn't need to sit there and think of complex dialogue, because stereotypes exist. There's no need for them to think of what Big-Titted Slutty Jessica is going to do at any given time, because the answer almost always involves a dick and her using various parts of her body to do things to it. There's no need for them to think of what Big-Titted Slutty Teacher Jessica is going to do at any given time, because the answer almost always involves a student's dick and her using various parts of her body to do things to it. I don't see most Western games "cleaning up their act" because of this. It's disgusting, shameless and, as much as I hate to use this word, objectifying, but it's what Western audiences are used to seeing in their porn, and writing cheap "dirty talk" is an effortless way to appeal to those audiences.

To be fair, I don't like the Eastern "no, don't touch me there, it's embarrassing" stuff much better because to me most of those scenes end up reading like the girl's unwilling and scared - yes, the exact opposite problem of Western dialogue - but at least cleaning it up involves nothing more than removing every "no" and "don't" and "embarrassing" and making some minor edits so it all makes sense. It's definitely not so fucked up and needlessly graphic that cleanup editing would be fully rewriting entire scenes because Sarah Slutstack can't go two lines of dialogue without mentioning her vajayjay being wet, or saying it's so hot that she wants to take off all her clothes and that's making her vajayjay wet, or lamenting about falling into a puddle of mud and getting all dirty so she needs to take a nice long hot shower and also that nice long hot showers make her vajayjay wet, or experiencing an earthquake or a really powerful explosion that shakes the ground and that all the shaking reminds her of her 30 inch vibrating double dildo and aw beans now she wants to go back home and use it because her vajayjay is wet.