I don't think this is shallow. It's part of our core human being to try and propagate our genes, and there are good personal reasons for preferring this over adoption as well.

Pregnancy can make it easier to relate to the child before they're born, at least it did for me (as a guy). I have considered adoption, but I do have a fear in the back of my mind that I might struggle to love the child as my own as quickly as I would love a genetic child. Sure this might not be completely rational, but I think a lot of the decisions w.r.t. children are emotional and more value driven rather than rational.