Yeah, because as we evolved romantic love has become a tool of nature to help propagate our species.
We rationalize why we do the things we do, but it all boils down to our instincts. Groups have a better chance at survival than those not in a group.
We say "it's not all about sex". Well sorry, but it really is. Even if we use contraceptives. We're hard wired to want to engage in the act, no matter what the means.