Colleges also realize that (1) not all students have access to AP courses; (2) not all students can afford the multiple AP exam fees; and (3) many students don’t take their AP exams until the spring of senior year.
On the other hand, all students have access to the SAT in their junior and senior years before applications are due, and the SAT offers fee waivers. (Let’s not get into the “SAT prep course/tutor” debate here.) And the SAT I at least is supposed to test basic principles, not the advanced concepts that are supposed to be tested in AP exams. (Again, let’s not debate whether the tests work as designed; at least this is what they are supposed to do.)
So the colleges consider the SAT as a more universal exam than APs, and they use APs to determine credit once the applicant has been admitted.