I can think of a couple of reasons for that. One, a lack of imagination. It's hard to think up alien worlds, alien cultures, and aliens themselves. Two, a lack of porn potential (to most people). Since most people like, well people, this creates issues when designing aliens. Both because the creator can have trouble getting into crazy sexy time aliens, but also the consumer. Doesn't exactly create incentive, and is why the aliens in this game are very human (to some people's displeasure, lol). Three, small market to begin with. Humans are self-centered. While they do enjoy the occasional romp into a creative sci-fi fiction, they generally like humanity to be included in the story and they want the story to be relatable. Honestly, some real aliens probably wouldn't be very relatable at all. Anyways, having to cater to humanity's desire to be included and have things be relatable limits sci-fi potential. Add porn into there, and it's even harder (at least if you also want it to be good).
I agree to point one: It's very difficult to create sexually attractive alien porn contents.
"Not relatable" or "Small Market" seems more like excuses. There are many ways to make alien contents relatable. Looking at the main stream game Mass Effect - the most loved / r34ed characters are aliens (Garrus and Liara).
Also, tentacles.
In many cases, when alien feels like "human re-skin", is due to lazy design (where dev just want to rope in alien trope w/o much efforts), not the concept itself.
Tho to a degree I guess you are right, Culture plays in a role here: how open-minded you are affects the acceptance of things that are "alien".
This loops back to the difficulty of creation - unique, alien while sensual and relatable.
Also the philosophy: why try to create something with a struggle, when there are easier and serviceable alternatives?
IMO it's the case for LO - if the dev only planned "occasional alien dick", they wouldn't hv created such large frame, nor put so much effort into alien designs. But then struggles on the continuation.
Similar reason why there are so many "Real porn", "3d assets flip / reuse" or "Furry" games: you don't need to be a genius to make a "serviceable" porno out of them.
Yes good 3d renders and furry arts still require good skills, but they are still easier than alternatives.
If you exclude them, the quantity will drop tremendously. Is it due to "small market" that people don't want porn games outside of these categories? Ofc not, it's just difficult to create one.
