Revisiting pop-up campers

Not relevant to anything here, but there is an entertaining tax aspects to the larger Hummer. (I am a tax professor. It is a dirty job, but someone has to do it.) There is a limit on how much you can deduct for a business vehicle. The point is to keep people from, say, buying a Porsche 911 and deducting the entire cost in the year of purchase, claiming it was 100% business. But to protect farmers, there is an exclusion for vehicles weighing over 6000 lbs. Guess how much the bigger Hummer weighed? Yup, over 6000 lbs. Hummer dealers used to pitch the tax benefits. So Congress amended the law to say in the first year you can only deduct $25,000 for SUVs. Not sure why they did not just exclude SUVs from the weight exception. Hummer lobby?