Seeing as Carnival Paradise is the only non-smoking ship Carnival built, it may be possible to conclude there is not a big demand for more of the same.
Some have said the casino makes less money, the bars bring in less and tipping is lower.
If Paradise were a huge success, surely Carnival (and other cruiselines) would have built more such ships.
Smokers have rights; non-smokers have rights. They co-exist on land; why is it so difficult to co-exist at sea?