To be incredibly reductive:

  - Some people are so disinterested in standardized tests that they never did a practice test or anything like it (this is me!)
  - These people get a pretty significant bump from taking the test a second time, from sheer familiarity effects (I didn't bother, but maybe I should have!)
  - It is unclear that extensive SAT tutoring does anything for anyone more than "force you to look at an SAT practice test at least once, and alert you to the fact that you are allowed to take the test many times, thus giving you a chance to choose the max of a naturally varying set rather than a single measurement"