These are called Houseboats. There are thousands of them on lakes and inland waters, as well as the ICW. In fact one of my neighbors has a 72 footer 16 foot beam with twin I/O--( better with outboards). No reason they could not be cats on aluminun or fiberglass pontoons--in fact some house boats are built that way. Only about 10% of boats are used regularly--and this is thru the entire spectrum. I have been on gangways where there were 50 boats in the 50 to 65 foot size range, and in the course of several years, only a hand full every went out of the slips. Prestige? Keep up with the neighbors? Status symbols? I think a lot of it is fantasy. Bob Austin