To a certain extent you are right, smokers do have less clout than they did 10 years ago. Many public places are now smoke-free and smokers have gotten used to that. They have gotten used to excusing themselves from restaurants for a smoke break or leaving other public places to smoke outdoors. However, a cruiseship is quite a bit different because people aren't only there for a couple of hours. It is their "home away from home" for 7 days or longer. Make smoking too restricted and smokers will just stop cruising. That in and of itself wouldn't hurt the industry because smokers are a relatively small percentage of the population, but when you consider the spouses, and kids, and parents, and cousins, and aunts, and uncles, and friends that cruise with the smoker, the numbers get much bigger. There are just too many other vacation alternatives for smokers to be willing to tolerate having to scamper around trying to find a place to smoke the entire cruise and their are still too many families that have at least one smoker where a non-smoking ship would be a vacation-buster.
Just ONE ship (Carnival Paradise) couldn't survive being smoke-free so there's no reason to believe that a whole fleet could survive. Probably someday, but not today.