According to a report on About.com, that is why hotels are going smokeless.
Why Are Hotels Going Smoke-Free?
In response to new information from the Surgeon General over the past few years regarding the dangers of secondhand smoke, requests for non-smoking guest rooms has been on the rise. Many smokers are also in the habit of requesting non-smoking rooms, increasing the demand. Marriott already had 90 percent of its guest rooms designated as non-smoking before the ban was announced; Westin had 92 percent.
For hotels, the benefits outweigh the possible loss of bookings from smoking guests. Smoking rooms incurred more costs for cleaning and repairs of burned furniture and carpeting. Also, having all rooms designated as non-smoking simplifies tracking available room inventory.