Im not a polygamist or anything but it makes sense though.

It keeps the man from getting oneitus

And it keeps the woman from losing attraction and getting bored Jealousy keeps the girl intrigued and motivated. Even if a girl has no sexual interest in a guy, but that guy has a girlfriend or two, she will be a little motivated to win his attention. But once she does win his attention and drops all other girls and commits she wil lose all interest.

What do u guys think about this?