For the same reason that Marijuana isn't legal. Special Interest groups. Who you think is in that congressmans ear everytime the subject of bio fuel comes up? It's the big oil special interest group man that's who. They don't want to:
A. Lose all that oil revenue to farmers growing plants for fuel
and
B. Don't want to have to spend the money to convert their machinery and factories over to produce a different substance.
They like it just the way they got it and until people really stand up and stop taking the shit it will stay this way.
