At the end of the day, its still an econobox. Its about cost savings. The lower end trims have 16" rims (steelies for the fleet or lowest end cars) with 60 series tires, the higher end cars have 18" rims with 45 series tires.
I saw one a couple days ago with 16" alloys and what looked like 50 series tires. They looked far too small.