Where do you propose that they drill more, and how do you propose that they get the EPA permits to drill?
Did you read my post for what it said? Here is how it works: the major stockholders of large oil companies shelter their income in private, tax-exempt "charitable" foundations. Those foundations make "donations" to NGOs and green groups that do everything they can to shut down drilling.
Need an example? Energy Racketeering: The Natural Resources Defense Council (NRDC)