Specifically, the Section 179 deductions available on vehicles that weight in excess of 6000lbs. A business doesn't need to prove need to make use of the tax advantage. This encourages real estate agents, sales people, etc to buy new large SUVs instead of leasing or buying second hand sedans that would otherwise be suitable (Mercedes E-Class, etc). And contractors that could use smaller vehicles (Transit Connect, Ranger) to buy F-150s or large vans.

It's basically a massive kick-back to Ford and Chevy.