It's simple, because he wants easier access to sex.
Think about it, for the majority of girls, sex isn't something that a guy can achieve in under an hour. Unless your both drunk and at a party. But for the most part, sex involves a lot of work. This mostly involves dinner, casual "get to know" conversations, and other activities.
"Remember how nice he used to be? He'll play that card again."
So yep, it's quite a bit of work, and it's not really easy on the wallet either. So this brought out a nice little idea in the ever-growing cleverness of the male brain, "Why not try to get in touch with the ex".
Chances are, and most likely, girls take much longer to get over their ex. This is the part where the ex can take advantage. Remember how nice he used to be? Well he'll play that card again. The "how you been" and "you look great" bit. While this still involves a little work, it certainly isn't as demanding as meeting someone new. With a few "hopeful" lines such as, "I still love you" or "I still care about you", he's hoping this will reinvigorate your feelings for him.
The next step is sex. And the basic "score" for the guys. Most likely an ex girlfriend will feel that having sex with her old boyfriend will drive him back to her. Wrong. The obvious reason is this. Men will seek out the easiest and most practical way to have sex.
"If you ever truly want to get over an ex, lose all contact with him."So remember this ladies, if you ever truly want to get over an ex, lose all contact with him in order to get over him. Otherwise he'll play the "easier relation" card.
"It's far easier and cheaper to go back to familiarity than it is to start anew".