Robyn Maislin sed "I think it's that we look more like "regular" people to motorists when we are not in full roadie gear, but honestly, I don't care what they think."

Exactly.

I don't care what they think as long as they treat me well and don't hit me.

Around here when I commute on my road bike the reaction/looks range from hostility (along the range of "WTF is THAT doing here, she should be in Woodside". I'm obviously very much seen as "other".) to curiosity which would be ok if they did not run across the BART station to grab my bike (in the "oooooh, it's so pretty" type of thing, true story).

When I'm on the MTB I'm just regular people, often waved through intersections and I like that.

I think there are some class issues involved is part of my theory. Since I'm not a sociologist I'll leave that be. And like Robyn says "I don't care what they think" if wearing a propeller beanie on my head makes me safer, I'd get one