Accepting Bitcoin is so easy and basically free that you must be an idiot to not accept it. All merchants ever don't accepting Bitcoin are just ignorant about it. They are losing on a potential economy that they don't even know to exist. I think most of them who have heard about it are waiting for a "snowball effect" to ensue.
Maybe people do not know about the benefits bitcoin, but the fact that porn will greatly benefit as well as the users themselves. Anonymity in selecting the most necessary porn.