That's because condoms and other ways of birth control weren't very common yet before World War 2. In third world countries, most people still don't have the money and possibilities to buy these things.
It's not just money. There's also that pope guy trying to brainwash Africa into hating contraception.
Bet Shiken that COD would outsell Battlefield in 2018. http://gamrconnect.vgchartz.com/post.php?id=8749702