I do understand the frustrations of the OP - I recall too many instances in the lower tiers of people just quitting.
Some people are simply bad losers, the hit one rank shot and they X out. Others want to "protect" their average (equally as lame IMO). Others are gamers, not golfers....where X'ing out seems acceptable.
As pointed out, completion rates can be seen in the game lobby - as a rule I will boot any random that is not in the "green'.
Your best bet is to add friends who do not quit and you get on well with. Country Club members are also another area where seldom will a fellow CC member quit a game - if they do without valid cause, I remove then and would report to the owner.
WGT will not punish their players - even quitters add to the coffers as a rule. I like the add a positive incentive, but I am not sure what could be added without players exploiting it (ie - if double XP were awarded if a quitter was involved, players would deliberately quit so their mate could level up faster).