The YES/NO is a waste of time for me because it's probably using a different threshold than I am. If I have all the free time in the world, I'll probably see everything 7.0+ as a YES. If I only have time for a couple of games a year, I'm probably waiting for a 9.5+ to give it a YES.
It's not a matter of if something is worthwhile, but how worthwhile it is. Had The Last of Us not been stellar, I probably would have waited some time to get on board, maybe even waiting for the eventual PS+ release. Since it got all tens, I knew it would be a topic of discussion amongst people and I wanted to be able to take part in that, so I picked the game up and played through it straight away.
Additionally, scores can prime a review in advantageous ways. For your average game, I probably have no great interest in actually reading the review. Describing mediocrity is often itself mediocre. So, if I see an unusually high or low score, I'm much more interested in reading the review to find out just how it arrived at that perception.
I won't pretend for a moment that review scores are the be-all/end-all, or that they are without flaws, but they remain important and integral to the industry.
edit: and another thing: it doesn't bother me in the slightest that reviews are top heavy, mostly in the 7-10 spectrum. Most games are pretty decent, compared to what they could be. Most developers are at least somewhat competent, and most publishers know when to drop a project that isn't going to be any good. Complaining about top-heavy scores is like complaining about a lack of short people playing professional basketball - you don't get to become professional by being terrible.