I guess because of college and med school where we have the USNews rankings to give student an inaccurate but quantified feel to school rankings, med students like the idea of rankings. Residencies are just like any other jobs, how do you know the law firm/banking firm you're working for is the best? You don't, but you will have a general idea about which ones are top of the line, simply by asking around, and you'll also realize that a lotta places are considered good. Yeah, you have no idea whats number one/two/three but you'll realize they're are many schools for a certain tier of quality(one is not necessarily better than another), much like jobs and even colleges/med schools, regardless of what USNews says.
