Individualism. I see the same problems in monogamous marriages as there are in polygamous ones. We're not taught to share anymore, we're taught to "succeed". That means more pressure, and more pressure means less time to enjoy, be yourself, and to share.
People who are less individualistic and more communal can still be monogamous, but they also tend to have stronger social bonds and lower incomes, making them more vulnerable. Bohemian lifestyles match this, too, and I've found more people in alt-lifestyles in these groups than I've ever found in a relgiious setting. (Utah excepted, of course, but we're talking about outside America.)
Individualism encourages one to compare a lot. Can you get a better job, house, car, husband, wife? "Change is the path to success." Who cares how that affects others, so long as you're happy. It also (rightly or wrongly) encourages one to assess and stand up for their rights (but not necessarily their privilege).
It's a real shame because I've had the overwhelming impression from my vast (pre-COVID) travels that the people I've met in the poly* community have undergone more self-development, understand the world better, have more empathy and compassion when it's needed, have more friends, and live happier, healthier, more fulfilled lives than the general community by several orders of magnitude.
I believe that's partly because they're not looking for "the one" or questioning themselves or the relationship. They already *are* in the relationship they want because they chose to be there in the first place. They have confidence to manage their own feelings and behaviour and negotiate their own needs and wants because they already learned those skills before they even got into their first relationship. They didn't assume anything. They didn't expect the relationship to "solve" anything for them. They accepted in some ways and encouraged in others.
But that could just be my bias.
