What is the underlying reason Congress doesn't want to increase our nation's oil supply, decrease our dependence on foreign oil and, hopefully, lower gas prices?
I think it's the fact that drilling in the off limits areas of the US won't make much difference.
The Energy Information Administration reported on the effects of opening up ANWR earlier this year. They estimated production would peak in 2027, at 780,000 barrels a day. Current US oil consumption is about 20 million barrels a day.
They predict ANWR would lower oil prices by about $0.75 a barrel, which would be about 1 - 2c a gallon for fuel.
The other off limits areas like around Florida and California, collectively, have less oil than ANWR, so will have a smaller effect.
Of course that doesn't mean they shouldn't be opened up for drilling, but what it comes down to is a minor, delayed benefit. Not much to attract politicians in that.