@lombok2: USNews rankings.
And colleges play this game because so many people are still suckers for USNews rankings. Both prospective students and alums.
For instance, UChicago saw a big rise in the rankings when it went from being one of the few holdouts in the USNews arms race (with the Uncommon App that deterred rather than encouraged lots of applicants) to being one of the schools that games the hardest. Expect Reed (which recently changed its philosophy of not playing the USNews game which it was punished for by being ranked far lower than other LACs who send a comparable percentage of grads on to PhD and elite grad schools) to follow the same trajectory.
Look at the example of Syracuse and NEU. 20 years ago, people would have put them in the same tier. If anything, they would have had Syracuse higher. But Syracuse disdained chasing rankings while NEU gamed the USNews inputs hard. Now you have top 2% kids considering NEU alonside much more elite schools because NEU has rocketed up the ranking. You don’t see the same with Syracuse (besides it’s long-renown communications/journalism school) because it’s mired lowly deep in the rankings.
Look at the example of USC. Several decades ago, the U of Spoiled Children was seen as a party school for rich kids who couldn’t get in to a UC. Now it is seen by some as being on the same tier as the elite privates because it has also gone up the USNews ranking by gaming the numbers.