MGB01: i think these quitters just want to piss someone off.
I believe the above statement to be correct. Although I have not had it happen many times, it still makes me wonder why they think it will upset someone. It is a childish act that can only be laughed at.
Even those who use chat, with their disparaging remarks, are fun to see. At least from my point of view. It is not very often one sees someone willing to open their mouth to show you how foolish they are.
Enjoy your friends. Enjoy the game. Enjoy those who attempt to ruin the game. It is they who are the reminder that you are in a better place in life.