A used car can show 150,000 miles and still make more sense than another car showing 90,000. Mileage matters, but the odometer cannot tell you how those miles happened, how well the owner maintained the vehicle, or whether an expensive repair lurks around the corner.
A car that spent years cruising highways may have endured less wear than one that spent the same number of miles crawling through traffic and making endless short trips. That makes the mileage question much more interesting than simply asking where the six-digit line appears on the dashboard.