Call me old fashioned, but when planning a smoking room in a Hotel, how difficult would it be to consult with your fire alarm engineer to identify which head is SD and which ones aren't??
With regards to the insistance of credit cards, a trend in many of the bigger Hotels I have dealt with in the last few years is the theft of their televisions from bedrooms. Guests arrive, pay cash and book in with their large suitcase which is just a bit bigger than the flatcreen TV in the room (!). By the morning, the guest has left with the telly from his room, and any other rooms left open by guests who have already booked out.
So while I accept there is opportunity for the system to be abused (as in the Belfast ridiculous £1600 charge case), I can see why Hotels prefer to use this system