The whole thing is complicated. When was the last time there was a plane accident where the hoods would have made a difference? There are liability issues with these things being stuck in every seat pocket, too. Odds are much greater over a given period of time that some kid would manage to suffocate himself with one of these hoods than of a life being saved in an accident.

That being said, smoke hoods do work under the right circumstances, and a frequent traveller could carry one of his own. Might not suck to have one in an office building or home either in case of fire. A huge number of fire fatalities involve smoke inhalation.

BTW, try to visualize the last time a plane went down in the ocean and all the passengers were bobbing around on those stupid seat cushions. I know a placebo when I see one.