Question says it all.
Most Helpful Guy
It depends on the scenario. If the women broke up with the man, then the man wants to show the woman that he can live without and move on. He tries to prove to her that he has found someone else and he doesn't need her anymore. Most of the times this is done unintentionally, but sometimes it's to show he moved on, or possibly trying to lure back his EX, once she realizes what she left.
If it is the man who left the woman, I have no clue. That one puzzles me, I don't see why they would do that in the first place, maybe to signal that now there isn't anymore chance of getting back together.
For the most part, the reasons it's done aren't good at all and are pointless and makes the man look ridiculous to drop to that level.0