Why is it so hard for married couples to ttc?

Cyndrea • Love God, Love my Husband, Love my family, MC-10 wks/August 18'.
My husband and I were talking.... How come it seems like unmarried people, who are not even trying for a child, can get pregnant alot easier than married couples. It seems like married couples try FOREVER! Why? Why? Why? And half the time people who get pregnant are really unsure if they even want a child while we over praying for one...