Pump gas is oxygenated with MTBE, ETBE, TAME and other lovely sauces. Are you suggesting that pump gas should be banned too?
The specific gravity of Chevron Supreme, according to the company's MSDS, is .7 to .8. This is a huge range, and it covers everything from VP C 12 at .717 to Special 5 and MR1 at .740. How can a specific gravity test distinguish between Chevron Supreme and an expensive, exotic fuel like Nutec? I don't think we want to start submitting fuel samples at the beginning of the season, do we?
Power gains from fuel are way less significant than those that are available through exhaust upgrades and jetting optimization, and a fuel's ability to improve lap times pales in comparison to that of proper chassis/suspension setup and tire choice. If the outcome of a race comes down to fuel choice, then the riders involved need to consider going pro. For the rest of us humans who race at the club level, fuel choice boils down to bragging rights, mental crutching and aroma therapy.