I wouldn't really describe it as a 'normal' procedure - it's a specific manoeuvre, trained for and employed in certain circumstances.
It would be great if we knew that all pax had the level of interest and understanding of those who bother to seek out PPRuNe, however in reality this is not the case. Combine the difficulties and low priority of pax communication in a non-normal situation with the difficulty of explaining such events with clarity, brevity and honesty, whilst not alarming less aero-literate passengers, and you can see the problem.
My airline has a automatic PA announcement which comes on when the masks drop and explains what is happening and what to do - if passengers miss this as well as failing to listen to the pre-takeoff safety brief then I am afraid that no amount of PAs from the flight deck are likely to help.