Reading (and posting to) one of the latest "Do ratings matter?" threads on BGG it occurred to me that there's a subtext here that bugs me. The argument usually starts as a generic "why would you care what other people think?" kind of thing but the subtext is that the enjoyment of other people (eg, your opponents) doesn't matter, and therefore other people's opinions don't matter.
Other people's opinions matter, because I play games with other people. If one has a limited circle of people you game with, they may be the only ones you care about, but I, and most people I game with play with lots of different people, and are constantly introducing new people to the hobby and playing with more casual gamers. Even this year, which has been a really slow year, nearly half the people I've played with have been "new people". So, to that end what a "random gamer" thinks matters, in that I play with a "random gamer" on average more than once a week.
In detail, over the past eight and a half years, I've played with two new people a week, on average. My wife, who I've played the most games with only has played in 25% of the games I've played. The next most frequent gamer barely breaks 10%. Over 50% of the people I play with, I only have ever played a few games with, so knowing what games a "random gamer" is more likely to like is useful. Of course I use my own judgment, but I can't always predict what's going to succeed and fail with other gamers. For example, I personally never would have realized the extremely broad appeal of super-hits like Ticket To Ride or Carcassonne, or realized how universally I should be careful about inflicting something like Vabanque on other people.
Of course, to repeat a comment from the above thread ratings are meaningful but not oracular. For a shared activity like games, other people's opinions matter to me, and ratings are one way to get some insight into the opinions of all those gamers who I'm going to play with who I haven't met yet.