US hysteria
20 years ago most of flights were smoker ones. The current situation is due to the US hysteria of non smoking everywhere. As most of marketing men and managers want to keep their US passengers, slowly all the flights became " Non smoking"
Good for the out flow valves which request less frequent cleaning, bad for some asian passengers used to smoke a lot, not used to fly and....go in the toilets for smoking, then triggering the alarm.
We have flown during half a century with passengers smoking on board, the most dangerous is to put the butt in the bin of the toilet and it is what are doing some old passengers not used to fly in our asian area. Thanks to the US hysteria!
(Personnally I am a non smoker since 40 years, but I am tolerant and accept smokers at the condition it remains at a reasonable level)