I think teachers/coaches should also teach their students tournament chess ettiquette .
Again, a wise coach will advise their students not to resign. For beginning to mid level players, every game is a learning experience. Resigning too early denies them the opportunity to learn.
If your expectation is that your opponents should resign from losing positions, then you should only play against high level players, who don't have anything to gain by playing on.
You don't learn anything being mated king and queen vs king. If you do, spend 5 minutes and learn it. You're wasting everyones time. If people resigned and spent the next few minutes studying, they'd learn a lot more than they do shuffling their king while their opponent promotes pawns.
Players who play on in ridiculously lost positions are themselves being rude and deserve whatever response their rudeness may provoke from their annoyed opponent . The truth is that good players know when they should resign and they do . Some children , some beginners and most jerks refuse to resign even when they should .