Just as a recent example for the above statistics: in this cycle, an applicant who was born in WA, lived in WA thru high school, has all their family in WA, has an LM of 78, had 100s of hours volunteering at a free clinic for immigrants, 100s of hours EMT, 100s of hrs of research, etc, etc, BUT took a job on the east coast after graduation and so (immediately) lost their Washington residency... did not get a secondary.
They've had an objectively great cycle, with over a dozen interviews including T10 and a half-dozen acceptances, so it's not like their application was flawed -- it's just REALLY hard to get into UW if you're not from WWAMI.