Some creatures are more monogamous or poly than others. I don't see why this can't apply to people as well.

I think most animals are wired to take on as many partners as possible. Propogate diversely.

It is illegal to marry more than one woman or man, but nothing in the law prevents you from living with several or having multiple partners, married or not.

While more common in men than women, I have known several married women who had multiple partners, one was married 3 times and "cheated" on all three husbands, although she and her present husband of about 25 years went into the relationship as an "open" relationship.

I completely do not get polyamory, but if it works for others, I say go for it. Just not for me. One person is enough work, ha ha!

Monogamy is not human nature. There is a really good book on the topic

Sex and God: How Religion Distorts Sexuality by Darrel Ray

If I act poly when seeing someone it means I'm not in love with you, period.
I think as with various creatures there are degrees of people more prone to "poly" than others.
Also seems very trendy right now. JMO
My kind is not. NFW am I gonna be poly caring for and wiping your --s on your death bed.
Nopety nope noping that from space. What a fustercluck that would be. Just no.

From my point of view it depends on the people, there are those who like to have more partner and others that are happy having just one,we have plenty of problems just couse of the society, with the freedom this questions wouldn't even exist xD