The first reason is because there is a lot of people who watch the show outside of the US. And the ratings that you're probably talking about, are only for people watching on The CW.
Second being the ratings used to be way higher, but the show is cruddy right now, so no one wants to watch.
posted over a year ago
Agree with clm-anomaly, I even skipped Nate, Chuck and Serena parts sometimes. I only watch GG for Dair.
@xochuckandblair: Actually, the ratings are slowly increasing because of Dair. "Gossip Girl saw the night’s biggest increases, up 23 percent in total viewers (to 1.6 million) and 20 percent in 18-34. (Dan and Blair, FTW!)" source: TV Line
You have to consider that from those 9 million there may be fans from other countries too. I don't have a facebook account but I am a fan and I'm suuuuure there are more in other countries. Besides, if you miss an episode or just want to watch it later for whatever reason, you can watch on the internet.
