Primarily due to the fact that environmental groups, through lawsuits and other means of obstruction, have successfully prevented the building of ANY new oil refineries in the US. The last new refinery was built in the 1970’s, and the existing refineries are nearing the end of their useful lives. Oil companies are even being prevented from replacing aging units on land they already own. You are seeing the results of this as old refineries are subject to catastrophic breakdowns, and “routine” maintenance takes refineries off-line for extended periods. Environmental extremists who hate fossil fuels and want to get you out of your automobile and into their government “mass” transit, have made it impossible to bring online new refining capacity, to make use of the increased volume of crude oil being extracted in the United States.
Results? $6.00/gallon gasoline, and domestic fuels being exported, since they can’t be refined here. Thank your local “environmental wacko”.