While many aircraft and airlines are non-smoking, there are regulations on designers to put a certain number of ashtrays per passenger on aircraft as a place to put a burning cigarette, should an ignorant passenger decide to light up in flight.
Would putting a burning cigarette in an empty beer can with water in it be better, most probably. But somebody gets paid to make regulations, and we must live by them.
Hope this answers your question.
Break ground, and head into the wind. Don't break wind and head into the ground.