Why do many men wait to propose after they get their partner pregnant?

I don’t know if it is my generation or if things have always been done this way, but it seems like maybe 8 out of 10 couples I know, got pregnant and had a baby and then got married.

I don’t see the point in men waiting til after if they’ve always planned to marry them some time in the future, why wait many years? Example, couple been together 5 years and no engagement, they have a baby, next few months get are engaged.

I would hate to think my boyfriend married me because he got me pregnant. We had a talk and he does see us getting married one day, maybe in the next 3–4 years. If I got pregnant, and he asked me to marry him 10 months later, I wouldn’t understand why much sooner just because we have a baby?

Do they think, “Might as well do it now.”?