Because, unfortunately, it is to the point where gasoline is a necessity, not a luxury. Whether I choose to go out to dinner or have a tuna sandwhich at home, or perhaps whether to buy that new computer game or not, can be based on price and market conditions. But, with few exceptions, I MUST have gasoline in order to generate income. If mass transit were the norm everywhere in America that might not be as big of a deal but it simply isn't the case. To get to my clients, I must drive my vehicle. To get to healthcare facilties, food sources, etc, I must drive and consume gasoline. I can certainly take steps to mitigate my consumption, in driving habits, vehicle maintenance, and even choice of vehicle, but ultimately I will still need gasoline.
All that rant is to say that gasoline isn't just a regular consumer good like any other that can happily ride the market ups and downs. I have no problem paying for gas and I have no problem recognizing that as raw materials costs rise so do the end product. That being said, the way the price rise, the frequency of change, and the percentage of profit from a good that I MUST have should be subject to more scrutiny than a Subway sandwich. Numerous other industries have their pricing and profits regulated, so why not gasoline?
If gas were something I could "take it or leave it", then I would be much more inclined to support a total free-market approach to its pricing. Since that's not an option, it needs to be treated differently.