Evolution of pregnancy in stories to modern times

It's interesting to read some stories on this site when they touch upon the topic of pregnancy. When the topic comes up the characters automatically assume they have to have sex with a guy and don't seem to ever even consider an alternative option. I don't think I've yet read a story that has mentioned in vitro pregnancy. I'm curious as to why that is? The characters never even seem to give a thought to the fact artificial insemination exists even though its been around for quite some time. So I wonder if its more just for a plot device or lack of knowledge in general? It seems like a pretty obvious thing to consider rather than just jumping to the conclusion that the only way to get pregnant is to sleep with a guy. I definitely noticed this in Fresh Start for example whenever they discuss the fact that Jirra can get pregnant, not once is in vitro mentioned. Overlooking such a thing seems to be a pretty significant flaw.

Is it the age of the story? Well possibly but again in vitro has been around for decades... its the entire reason why sperm banks exist.

So maybe some one can help answer why this seems to be? That or maybe most stories do mention it but I am just not reading those ones.