Score rating is pretty much a useless stat nowadays because it's only used to determine your tier ranking. There is no ranking for score, so penalizing something that's already kinda useless won't help much. It's also a double-edged sword because if you start adding penalty points, then you've made it that much easier for the real sandbaggers (those who post rounds of +10 purposely to keep the avg UP to avoid the master tier) to do their thing. At least now those players have to put some effort and wasted time into tanking their scores on purpose.
Right now if someone quits, it's just "oh well, that sucks". No advantage gained and none lost because it usually won't kill the game and even if it does, you can choose to resume in single player.
Folks have requested a separate stat to track it, WGT has said they are "looking it over". We'll see.