Because a Halloween weekend is totally representative of the game's normal traffic ...Oh who am I kidding at this point?...
That number is counting how much people are logged on at the same time. This isn't indicadive of how much people play the game during a week or whatever. The actual number of people following this game is actually much higher. Still, it's still depressing to see that number so low.
Also, sorry about the two consecutive posts, but attaching files and these forums don't get along super well.