I was surprised in Seattle by a line of carriages waiting for costumers (not too enthousiastic).
I read that it is a tradition in holidays (it was almost Christmas when we were there), maybe more fun with snow, that we hadn't.
Not cheap, however...
It's considered a romantic way to see the city, but I feel sorry for the carriage horses in big cities these days...the traffic, noise, air pollution is almost unbearable. This beautiful carriage horse was obviously well taken care of, but his owner/driver said that he is somewhat deaf because of the incredible noise level of the nearby traffic. The little green covers on his ears are to help block out noise and to keep the flies away.
I can never bring myself to hire a carriage for the guilt it would bring me to cause the horse more work and possibly put him in danger.
On my last trip there, for some reason, we kept seeing art representing pigs around the city. My roommate dared me to 'ride the pig' in front of the marketplace.