Because the perception is that these schools allow you access to jobs, such as I-banking, wall street finance, and business consulting that allow you to potentially climb the SES ladder and escape the grinding mediocrity and despair of middle class existence without having to go to med school and get one of the ROAD specialties. (I think I have this one right.)
Well, that and they *are* important if you have the insane idea that you want to go do law school because the status of a Good School makes it much easier to get into to a Good Law School. It's kind of entertaining to watch the entire Law School Complex slowly implode, but that has nothing to do with this.
What's interesting here is that the desire to get into such schools because of how the game is played after college is the very reason many people are complaining about getting into that college.....how the game is played. We could take this a step further with, "It's unfair that getting lawyer positions are based off of where one goes to college, it should be based off of the bar exam scores and nothing else!"
If the game wasn't played that way with a specific college determining / helping to determine who gets those high paying jobs, then there wouldn't be such a big deal about getting into Ivy League schools and we wouldn't have to worry about making made to order admissions applications. There's a top down problem for people to solve.