How many non-smokers won't stay in hotels that allow smoking rooms?
The OP argues that hotels that don't offer smoking rooms may lose business from the 19% of the population that smokes. Likewise, I could argue, that 81% of non-smokers may not chose to stay in hotels that allow for smoking rooms.
Who is really to say which percentages are in each camp? For some hotels, it is a calculated risk not to offer smoking rooms. For other hotels, it has been forced on them by legislation.