On the main topic I never really got the appeal of preggo content in these specific games (other than the actual sex scenes where it happens and some of the flavor stuff during the pregnancy as waifu content) considering the kids don't factor in to an almost silly degree. In this particular one you literally just dump them off with a robo nanny so they don't cramp your space whoring style; they're p. much an elaborate "aww that's cute okay done with you now" sequence with hilariously douchey implications if you were to take it even halfway seriously.
Is the impregnation part of it just -that- popular among this crowd?
There is an irresistible force meeting an immovable object problem in porn games. It goes like this:
1) Pregnancy is a big fetish. You could say it's
the fetish, when you get down to it. Both male and female players want to see it, in various different ways. If you don't have the ability to stuff the player character/their favourite slut with spawn, your base is bound to demand it.
2) Children in porn is a double red line.
Unless your game is very simple and/or heavily homo orientated (and often not even then), you've got to come up with a way of surmounting this. I think TiTS' solution, of a safe zone where kids are immediately placed upon birth, and where cute content could feasibly go if anyone's willing to write it, is actually one of the things it's done very well, at least in principle. It certainly beats what most smut games do, which is have the kids only in bad or good ends.