It's what I do....
It's what I do, too. It's probably what quite a large percentage of members of this forum do. However, for the average punter it's clearly not the obvious thing to do, otherwise more of them would do it. I doubt the stickers about the environment are noticed by more than a tiny fraction of the passengers either - but that's not to say they aren't a good idea.
I guess it could be added to the
TM‡'s announcement scripts, but I think the majority of us want those reduced, not added to!