I think it helps you know what words you rank for and where your traffic is coming from. i.e. if you see that a particular site(that you never heard of), sent

I think it helps you know what words you rank for and where your traffic is coming from. i.e. if you see that a particular site(that you never heard of), sent you 200 people, where each person went through 6 pages, compared to your average of 2...you know it's probably a good idea to go buy some ads there, since you know that site's audience will convert