[xwdv]

The irony is that modern society has made great strides to promote relationships between all combinations of genders of individuals... but any suggestion of non-monogamy is still struck down with shame or castigation almost reflexively, with little to no thought. It’s getting better though.

[r00fus]

There is no irony other than the fact that you think it's ironic. Monogamy is the default for same-sex couples as well. Orthogonal issue.

The issue with non-monogamy is that a pairing (2 people) is the smallest working group, and that's what the game theory of dating proves to be most durable and successful. A 3-person working group requires at least 3x more relationship work, and a 4-person pairing requires 6x as much.

[Twinklebreeze]

Polyamory doesn't have to be a three or four way free for all. One person could have two independent partners. Some partners will come and go, while others stay. It is more work, but it doesn't have to be as bad as you make it out to be.

[ngngngng]

It is ironic. I have no data on this, but I would guess that having sex with the same gender is far less common than having multiple sexual partners, so why have we worked so hard to normalize and legalize same gender relationships while giving no thought to polygamous relationships?

[empthought]

The legal frameworks have to do with property transfer and responsibility for raising children, both of which are much more complicated in relationships with more than two partners.

[xwdv]

People have partners on the side very successfully until they are caught, and arguably those side relationships would be more successful if they did not have to keep them a secret and their other partners agreed to the open nature of the relationship.

[damnyou]

That relationship work you're talking about has some side effects that might be desirable, such as making you a better person.