This is a great question! It’s actually interesting that we have men at all! In many species, there are only women, or hermaphrodites (with both male and female parts). These animals are able to reproduce on their own and still exchange genes. 🙂 It’s surprising that men in humans don’t still have the ability to have babies, but we evolved in a way where males still care for children for a long time. This is why we think that we have non-pregnant males, because they care for the children.
A cool example of a pregnant male (which is really rare) is in seahorses!