And - in person, when people can't tell what gender someone is, they don't guess, unless they feel able to rely on visual cues or maybe being married to someone of a known gender (and when they are wrong they are mortified). People will bend over backwards to avoid using the wrong pronoun for someone who's in the room with them. They'll ask third parties or construct their sentences to avoid making the assumption or learn the person's name to get a clue. It's just not socially acceptable to get it wrong.

I'm pretty sure that's a function of where you hang out.

My impression is that transgendered people have a hard time getting their choices taken seriously in most social circles.