Ian W...
Perhaps it is time to tell airlines that briefing SLF particularly the SLF that need to be told how to do up a lap belt may mean making things a little more formal.
Passengers' almost complete absence of situational awareness goes along with wearing flip-flops, T-shirts & shorts when departing for sun destinations from northern airports in mid-winter. I'm not sure what the survival time in -28C weather even with no windchill factor is but an evacuation isn't going to be very comfortable in light shirts with palm trees on them, and flip-flops don't give a lot of protection against sharp metal edges or rough ground just in case things go pear-shaped.
Why ruin the fun?, marketing reasonably says...what are the chances? Well, it works okay until it doesn't. It takes so little effort to take some of the responsibility for one's own safety aboard an aircraft.