The answer is.... They don't have to!
It is a necessity. (Falicy) Everyone needs it!
Let's look at supply and demand.
The demand has grown a lot higher since the prices have been going down. The demand is also much higher since the 90s considering there are more people driving today than before. Typically when demand goes up, so do the prices. But they are competing with a group that is making it so cheap that OPEC must compensate to compete which means every other gas company must do the same. Inflation and taxes are one factor, the US having its own gas is a factor. You could make the mathematical arguement that $2.20 today is equal to $1 in the 90s. Don't know the math but it's probably somewhere close. OPEC is nervous right now because they don't know what's going to happen.
But, they still want to make the highest profit they can while meeting their quota, therefore, they do not really need to lower prices nore do they want to unless the other group continues to out compete them with lower prices in the market. Essentially we commend that other group for doing this, but at the same time they are Evil and even more corrupt and we all want them to die. Soo who knows how long these prices will last.
What will America do? If we build that pipeline, it will be game over for mannny oil companies who supply to the US. So OPEC has been worried about that as well.