I wish they would do this when you're boarding the plane. I get that there is essential information that everyone needs to know, but if you're a frequent flier you've probably heard the "put your larger carry-on in the overhead bin and your smaller bag underneath the seat in front of you" hundreds, if not thousands of times.
Especially flying with kids at naptime or bedtime. Trying to get an extremely tired toddler to fall asleep on a plane just to hear an announcement about in flight entertainment. OMG.
There is a large and growing population of people leaving their home country for the first time ever, let alone by plane.
That particular rule kinda depends on the airline and how full the flight is
There is apparently 10000 people every day who learn about it for the first time, according to https://xkcd.com/1053/
Much much worse are the repeated advertisement “announcements” about signing up for their credit card or frequent flyer program
There's a large subpopulation of people flying who seem to have no idea how planes and airports work. Maybe they're sleep deprived or it's their first time flying, but these announcements are targeted at them.