The question is price. Air travel 'sucks' but has also become a lot more accessible, even long haul. If an airship takes 4 days and costs the same as business class on a regular plane I think many people will just business class.
With that kind of thinking there would be no market for ocean cruise ships - but there is :)
Perhaps people could be convinced to take an "air cruise", though it'll never have the amenities of a ship, but as transportation there's very little room for slower and more expensive.
Slow float over Mt Everest.