I'm realizing, at this moment, why people use "Significant Other".
It takes all kinds to run this world, and not all of us are married, and not all of us are married to the opposite gender.
That just seems like a strange greeting to a new person, especially if they don't fit into the same box as most of us.
As a rule, I keep S.O.s out of the conversation, because nothing riles a person up like a compromising view about their partner.
I even think twice before posting about family at all.
Recently a guy tried to insult me on a guitar forum, something about me not taking care of my wife. That said more about him than it did me, since he had no idea that I am perpetually single.