Why are they so eager to commit into marriage? I figured out it is because

a) they want a family, and having a child without being married has a general negative connotation in today's society
b) they want their partner to commit fully; their boyfriend could just get away, whilst their husband ought to divorce (not as simple) or stay
c) by marrying a man, it is the 'ultimate' way of displaying love

Not sure if these ideas are right. Correct me if I'm wrong, or give any other ideas.