It has nothing to do with oil companies. There are already some vehicles that burn natural gas for fuel. They are used in short range situations where environmental sensitives run high. There are conversion kits available. Unfortunately, it is impractical for most of us.

Unlike propane, natural gas doesn't liquefy at ordinary temperatures, so that limits the amount of fuel that a vehicle can carry, and that in turn limits the range, which limits the vehicles usefulness. Then there are the questions of distribution and infrastructure, not to mention adequacy of supplies, if everyone was burning it for fuel.

Natural gas simply has a limited place as a vehicle fuel.