That is your situation. I find we all read threads by our own bias. Our own situation. This was a general question, and I was posting my views as such. Believe me, I understand not everyone falls into that general situation.
Just as I see posts that seem biased towards couples that become poly or move into poly. Stated as unicorn hunters, which DH and I have never been, or the rudeness of how dare married couples get involved with other people because there is a hierarchy already established. Just as I see people bash mono/poly relationships as unfair. It happens with everything. So perhaps the OP questions have different answers for you specifically. I've seen it go both ways, though typically more one way than another.
The situations don't follow my own either, but generally, that is what I see, on this forum, on other forums, on poly/mono lists, and in real life.
Me: 40 pansexual poly.
DH: My husband of 21 yrs and father of 3 teen girls.
DC: LDR of +9 years/former