Someone mentioned up thread that one of the problems is that for the very top students in the US, there might be 10 or 20 institutions to choose between and apply or not as the Case may be, and the need to finds compelling reason just why you and Yale rather than you and Princeton are a perfect fit, whereas in a country like the UK, you'd mostly choose between oxford and Cambridge (and you can't apply to both), maybe wonder a bit about UCL or LSE. Without even going into the nitty gritty of holistic admission versus exam driven admission, it makes the whole process so much more arcane and stressful. You might be accepted by all ivies by a fluke, but just as well rejected By all ivies by a fluke.