Well, some people are doing it to be chic.

But some do it because they get into what they think is a monogamous relationship, but then their partner suddenly announces they want to see other people as well, and they are too into this person to just let them go, so they sort of get talked into the whole poly thing when it really isn't what they want.

what amazes me the most is how openly yoda was into wookies.

granted they say with hundreds of years of age, comes a bit of maturity.

That's really unfortunate.