That's because the risk of pregnancy was greater. With the pill, why buy the cow when you can get the milk for nothing? Once upon a time, when a man had a burning desire for some woman he had to propose marriage to get under her skirts and often followed through with it, especially if the woman wouldn't give it up without the actual ceremony.

These days it's way more likely that a man will knock up some slut and leave her hanging to either have an abortion or raise their spawn on her own--another topic for another thread.