Also there's general argument that sex is fun and pregnancy is end of fun
You can have sex during the pregnancy, you know. And again, that always happens in games in later stages, with high amount of corruption, so it doesn't sound bad at that matter.
I do understand that for author is hard to create proper content with pregnancy. But wonder why no one is even trying? I mean in VN and Ren'py. For inspiration, you could google pregnant Karla Kush videos - she's stunning, amazing and beautiful. So i don't really see why is it so hard to create cute pregnant girls in the games. And in some game we see them..but that's the end of content always. I'm just sad about this.