I think it's just a lack of understanding and familiarity. And of course people get into them for the wrong reasons and that can be disastrous. I struggled to get my head around them for a long time, especially since I was in a monogamous relationship and I saw that as 'the way'. But relationships change and 16 years into mine things have opened up (some what). I had a *really* weird year on top of the pandemic. A total head fuck. It's also worth noting that there isn't one way to have an open relationship. It very much hinges on what the individuals want.