Because smart guy, coal is:
a. not a renewable resource
b. extremely polluting to the environment, even in the case of "clean coal".
The whole point on coal is that we're sitting on all this coal and doing almost nothing with it because of (B), when it could be turned into oil and used as oil as opposed to continuing to import foreign oil. The best part is CTL plants generate less CO2 than oil refineries, and could generate almost none if the appropriate CO2 caputuring devices were used at the plant. Also, the wonderful thing about CTL plants is that they can be easily converted to turn any ordinary biomass into oil, meaning that in the long distant future when we have used up all of our coal, the plants can still be used to turn other things besides coal into oil.