''I Missed My Period'': Guys Still Surprised When They Hear That?

So many guys will have unprotected sex with their girlfriends over and over again and when their girlfriends tell them that they have missed their period, they will be looking surprised. Why?

Girl: i have something to tell you.
guy: what is that again? u want to ask for money again? didn't i give you 10 thousand naira last week?
babe: it is not about money. can u guess?
guy: guess what? i'm not good at guesses.
babe: i missed my period.
guy: Am I your time/period keeper?? Please stop this joke.
babe: it is not a joke. i am 6weeks pregnant. Iam with your child.
guy: (looking surprised), how come? how
manage? When??? are u ok? did i tell you that i want to become a father now?
and lots more.
funny tins.
why are  guys like this?