Rockmelt/Flock browsers

Maybe I'm dense. Maybe it's the sugar crash. Somebody's trying to explain the benefits of the Facebook-centric/optimized for Facebook browsers Rockmelt and Flock. To me, all you'd need to do is either open Facebook in a new window or a new tab, not download an entire browser. I also tried to read an article on Flock, but all it did was create a nice breeze as it blew over my head. Am I missing something?