I understand your frustrations... there are ways to alleviate this problem.
- Join the ladders ... www.wgtls.co.uk
- Play with friends only
- Play Matchplay Challenges (when they quit, you get paid!)
- Don't play random pick up games.
Having said that, please understand that this is 'just a video game'. People will leave for whatever reason suits them at that time and there is nothing you, personally, can do about it. You can not equate this video game to actually stepping out on the links for an afternoon with your foursome, complete with bad jokes, a bit of teasing, some alcoholic beverages, and the occasional "stick-em!" shot of the day. The only thing this video game has in common with a day on the links is they are both called 'golf'. As much as we like WGT, warts and all, even on it's best day it still falls miserably short of the real thing.
IMHO, the worst day on the local chewed-up-and-spat-out muni still beats the best day online.
Also, I can assure you that "quitting to protect an average" does more harm than good. These folks will make it to the highest tier by posting all of their best rounds, only to find that they can't compete anymore. And the folks that are already in the Master tier can't protect their average anymore, because once you make Master, you can never go back.
So, if someone quits it's ~their~ problem, not yours. Play on. Shoot the best score you can and worry about making your own game the best it can be.
Of the points above, if others quitting really irritates you, I will strenuously urge you to join the ladders. Great fun there, lots to do besides play golf, and I can almost guarantee that you'll have at least a dozen new friends that you WANT to play golf with in less than a week.
Have a 'quitter-less" day!