I think that they do it for three main reasons. 1)The romanticism of "my wife and child are waiting at home for me", or from the moo's perspective, "Poor me, all alone, hubby off to war and I am in calf", 2)To solidify and protect a shaky relationship. From the duddy's perspective, if she is knocked up BEFORE he leaves, then even if she fucks around on him, he can be certain that it's "his". Also, a woman will be less likely to get bored lonely and leave nothing but divorce papers behind for him to sign when he returns, IF she has had baybee to fawn over. From the moocow's perspective, he is MUCH ,more likely to come home, RIGHT home too, if she has a sprogglin awaiting hs return. and 3)From the male's persepctive, if he dies then he has left a genetic marker and can "live on", like they say. From the moo's perspective, she will get a WHOLE lot more money from the militay insurance death benefits IF there is a kyd.
She will also get TONS more sympathy and attention if she is left a widow while in calf, or shortly there after. This alone, earns her a place in the military moomartyrdom ranks and she is likely to get marriage proposals from numerous military men in comparison to only having been widowed or divorced from one, while not in calf or freshly loaved. There is an unspoken sympathy card for military widows, ESPECIALLY young ones who are/were in calf when their man was killed. I have observed that they usually get promoted rank wise, when they remarry. It's almost considered impolite for a man who is of a lesser rank to call on a military widow and it's nearly always a same rank or higher when they remarry. I grew up in a military town where Maxwell AFB is located and later lived in another military town within a few miles of Ft Benning Army Base, so I saw quite a good bit of this. Oh, a military man getting killed while on active duty in a war trumps his getting killed while in training or en route or otherwise not on active duty while in a combat region, and active duty but not during wartime trumps his death from non military accidents, in the world of martyrmoodom. I know all that sounds cruel, but I am not the one who created the ranks of the military moomartyrdom.