The higher up you go on the LS food chain the easier it is to get a biglaw job.
The lower you go, the more grades and school location count.
Because half of the USN rankings are entirely subjective (Judge/lawyer, what do YOU think about schools XYZ?) it is better to go to one that is perceived to be of higher quality than one that is perceived to be of lower quality.
Does it really matter what the differences are between CLS v. NYU v. Chicago?
I didn't even apply to NYU because if I'm moving to NYC, I'm going to a Ivy dammit. And let's face it: many (but not all) of the perceived differences between the *top* schools are ideas propagated by the schools and their alums in order to create chasms out of minute differences between programs. It's like shopping for jeans. I picked CLS because it had a fun design on the back pockets while someone else picked Chicago because it's bootleg. Very similar with small cosmetic differences.
Is the ranking system accurate-ish? Maybe
Is it helpful? Yes
Does everyone have to play the game regardless simply because that's how it is played?