Because they don’t like you enough to commit. Or at least they don’t like you enough at that moment in time. And, fascinatingly enough, because their brains haven’t wired themselves for commitment yet. Along with mapping the brains of infatuated couples, scientists have also mapped those involved in serious relationships. Apparently, scans of couples involved in LTRs showed activity in an area of the brain linked to long-term commitment.

• Dated someone who won't commit? Dish and bitch!

What’s even more interesting is that scientists at Emory University in Atlanta have been able to isolate an element that turns promiscuous males into committed males by activating this particular area of the brain. So far, the experiments have been conducted only on a ratlike animal known as a vole. If they are ever able to put that formula into pill form (Commitra? Fidelis? Lovium?), my guess is it would outsell Viagra in about three hours.

What often happens, of course, is six months after you break up with your beloved commitment-phobic, you find out they’re getting married to somebody else. What’s up with that? In a word, timing. A lot of people will say they’re not into marriage or commitment, but truth be told, it’s just that they’re not ready for it yet. Whether they’re not ready for it with you or not ready for it ever is up for interpretation.

For many people, getting married is all about finding the exact right person—once you meet them you marry, whether you’re 26 or 46 or 66 (the age at which Gloria Steinem married for the first time). But others are less discriminating about the person; it’s more a matter of finding the right time. They basically date around (some would say play around) until they’re tired, and then they just grab whatever looks good and settle down with that. Although this is frustrating for those who invest a lot of time and energy in a relationship without seeing it come to fruition, that’s life. As Peter Post says, “You can’t make somebody like you.” More importantly, why would you want to?