Why Do People Stress So Much Over the SAT?

High school seniors are being bombarded with warnings to study or take cles for the SAT. I know that's a test for colleges, but isn't it like any other standarized multiple-choice, timed test? I imagine it'll be similar to the Star Test or the High School Exit Exam (only, there's an essay). No one ever studies for those important tests, and they still do fine. Is the SAT THAT much harder??