I don't think I've ever seen a straw boater in the wild, on either side of the pond, outside of costume parties and barbershop quartets. I think to all intents and purposes they are dead. I also can't think of a single occasion to wear one in today's world where a well made and shaped panama wouldn't be a better choice, QED the photo above.
I can see wearing one to a baseball game just like they used to do in the old days.
I'll do it yet this summer when I get enough extra money (to get the hat and go to a game).