Maybe some very old fashioned notions of what constitutes masculinity. Back before the AIDS crisis of the 80s, it was fairly normal for men to be very very hesitant about wearing condoms - fearing that this would compromise said masculinity as well as being uncomfortable. And unplanned pregnancy for their wives/girlfriends was a validation of that same masculinity and was something to boast about. Attitudes like that stink on ice nowadays, but still happen.