Why is the USA tax dollars being paid to oil companies like Exxon?

Subsidies???Why is the USA tax dollars being paid to oil companies like Exxon?
The energy bill referenced below contained $2.6 billion in subsidies for the oil and gas industry, at a time when they are recording record profits. Big oil bought the US government through campaign contributions.Why is the USA tax dollars being paid to oil companies like Exxon?
Because they contributed to the campaigns and to the ';retirement funds'; of the legislators.
care to sight some sources?