Where are all the players?

I am a bit confused. When I look at the SteamDB website, it says that right now there are 647 players playing the game. However, when I look at the ranked servers list, I can only see 16 players. I know there are many non-ranked servers, but even when I look at the multiplayer page, I see semi-empty servers more often than not. So where are all the hundreds of racers?

Are there other private servers, communities, etc. where people meet?

I like ranked races, but I all considered, I would prefer fuller grids.