I may not be correct about this, and it may vary between locales. But I've read that current tax structures encourage the purchase of heavier vehicles. The deduction people can claim makes up for the higher fuel cost due to poor fuel economy.

The IRS Section 179 tax deduction encourages businesses (and everyone else) to purchase heavier vehicles. Business vehicles with a gross vehicle weight over 6,000 pounds qualify for the full Sec. 179 tax deduction. And vehicles over 8,500 pounds Gross Vehicle Weight (GVW) do not even have to display EPA estimated fuel mileage or a Monroney sticker nor are they subject to state emissions testing.

Gross Vehicle Weight Rating (GVW) is NOT the empty weight. It is the weight of a vehicle loaded to capacity with passengers and full tanks of fuel and oil. Note that ALL 3/4- and 1-ton trucks and SUVs exceed 6000 pounds GVW. Usually a V-8 engine with a matching heavier duty transmission and rear axle will enable a 1/2-ton vehicle to exceed the 6,000 pound GVW rating.

IRS Section 180F allows one to claim full depreciation for UNLOADED vehicles less than 6000 pounds. Note that ALL 3/4- and 1-ton trucks and SUVs are also under 6000 pounds when unloaded. The deductions are so significant that ordinary people might start a business just so they can claim the deduction on their taxes. The deduction they claim makes up for the high fuel cost due to poor fuel economy.

Tax deduction for heavy vehicles

SUV tax deduction

How many of these are zooming around with only one person in them?
AMERICAN GENERAL
MAKE · MODEL · GVWR (lbs)
HUMVEE · HUMMER · 10,300–12,100
BMW · X-5 SUV · 6005
CADILLAC · Escalade · 6100-6800
CHEVROLET · Suburban 1500/2500 · 6800-8600
CHEVROLET · S-10 Pickup · 4200-5150
CHEVROLET · S-10 Blazer · 4450-5300
CHEVROLET · 1500 pickup (half-ton) · 5600-6800
CHEVROLET · 2500 pickup (3/4 ton) · 7200-8600
CHEVROLET · 3500 pickup (1 ton) · 9000-15000
CHEVROLET · Astro Van · 5600-6100
CHEVROLET · Tahoe (half ton) · 6100-6800
CHEVROLET · Lumina Van · 5126
CHEVROLET · 1500 G-Van (half ton) · 4900-7100
CHEVROLET · 2500 G Van (3/4 ton) · 7300-8600
CHEVROLET · 3500 G Van (1 ton) · 8600-9500
CHEVROLET · K1500 Blazer (half ton) old model full size Blazer) · 6250-6450
DODGE, CHRYSLER AND PLYMOUTH · Ram Van 1500/B150 (half ton) · 5000-6010
DODGE, CHRYSLER AND PLYMOUTH · Ram Van 2500/B250 (3/4 ton) · 6010-6800
DODGE, CHRYSLER AND PLYMOUTH · Ram Van 3500/B350 (1 ton) · 7500-9000
DODGE, CHRYSLER AND PLYMOUTH · Dakota pickup · 4480-6400
DODGE, CHRYSLER AND PLYMOUTH · Durango SUV · 6400
DODGE, CHRYSLER AND PLYMOUTH · Ram pickup 1500/D150 (half ton) · 5000-6400
DODGE, CHRYSLER AND PLYMOUTH · Ram pickup 2500/D250 (3/4 ton) · 5126
DODGE, CHRYSLER AND PLYMOUTH · Ram pickup 3500/D350 (1 ton) · 10500-11000
DODGE, CHRYSLER AND PLYMOUTH · Caravan · 4340-5420
DODGE, CHRYSLER AND PLYMOUTH · Ramcharger · 5600-6400
FORD/MERCURY · Explorer/Mountaineer · 4780-5640
FORD/MERCURY · Excursion · 8500++
FORD/MERCURY · Expedition · 7000-7200
FORD/MERCURY · Bronco 4x4 · 6050-6300
FORD/MERCURY · Aerostar van · 4700-5380
FORD/MERCURY · Econoline van E150 (half ton) · 5500-7000
FORD/MERCURY · Econoline van E250 (3/4 ton) · 7200-8550
FORD/MERCURY · Econoline van E350 (1 ton) · 9300-11500
FORD/MERCURY · Ranger pickup · 4180-5140
FORD/MERCURY · F150 pickup (half ton) · 5550-6550
FORD/MERCURY · F250 pickup (3/4 ton) Pre 1999 · 6600-8800
FORD/MERCURY · F350 pickup (1 ton) pre 1999 · 8800-11000
FORD/MERCURY · F350 Super Duty (1 ton) pre 1999 · 15000-17000
FORD/MERCURY · F250/350/450 Super Duty (1999) · 8800-19000
GMC · Suburban 1500/2500 · 6800-8600
GMC · Sonoma pickup · 4200-5150
GMC · Jimmy · 4450-5300
GMC · Sierra 1500 pickup (half-ton) · 5600-6800
GMC · Sierra 2500 pickup (3/4 ton) · 7200-8600
GMC · Sierra 3500 pickup (1 ton) · 9000-15000
GMC · Safari Van · 5600-6100
GMC · Yukon (new style, half ton) · 6300-6800
GMC · Lumina Van · 5126
GMC · 1500 G-Van (half ton) · 4900-7100
GMC · 2500 G Van (3/4 ton) · 7300-8600
GMC · 3500 G Van (1 ton) · 8600-9500
GMC · K1500 Yukon (half ton) old model full size Yukon) · 6250-6450
JEEP · Grand Cherokee · 5700
LAND ROVER · Range Rover · 6050
LAND ROVER · Discovery · 6035
MERCEDES-BENZ · M320 · 6005
MERCEDES-BENZ · M430 · 6005+
TOYOTA · Land Cruiser · 6470
TOYOTA · T-100 pickup · 5700-6000