I see it as different from chartering.
I think of chartering as: "I hire a boat (and crew) to go sailing."
Whereas I see the BnB concept
as: "I spent two nights on a yacht in a wonderful location."
When I lived in San Francisco
years ago, I looked into buying
a houseboat in one of the famous houseboat communities. Each boat was very different, some with extreme 1970s styling. One I liked was 3 levels, with huge circular windows and domed skylights and very open wood interior
. It would have been a very cool place to stay as a guest if one were visiting SF. Some of the yachts in the Bay Area are beautiful old woodies that are historic and would be fun to stay on if one is a sailor and likes the style or traditions.
So, I could see lots of potential for special boats or old boats or big boats or historic boats with or luxury boats without hosts aboard.
And I don't think it has to be seen as a "low cost" stay either.
For example, I would stay on the Maltese Falcon, without expecting it to be low cost.