Why the Whopping Huge Tax Breaks for Big Oil?

The top oil companies have a record of having profits in the billions of dollar range per quarter. But that does not stop the Federal Government from handing them huge tax breaks and subsidies. British Petroleum was writing off 75% of the cost of leasing the foreign-flagged oil rig[1] that it burned and sank, thanks to Federal tax breaks:

According to the most recent study by the Congressional Budget Office, released in 2005, capital investments like oil field leases and drilling equipment are taxed at an effective rate of 9 percent, significantly lower than the overall rate of 25 percent for businesses in general and lower than virtually any other industry.

And for many small and midsize oil companies, the tax on capital investments is so low that it is more than eliminated by various credits. These companies’ returns on those investments are often higher after taxes than before.

Nine percent. The oil companies pay a lower tax rate than the janitors who swab the lobby floors in their office buildings.

How is this anywhere near approaching "fair"?

[1] The Deepwater Horizon oil rig was registered in the Marshall Islands. If we are going to give out whopping tax breaks for leasing oil rigs (BP was writing off $225,000 a day) we should at least make them hire US-flagged rigs in order to so rob the rest of us.