Because you should tax the thing you want to stop. Burning carbon is absolutely fine, provided the carbon originally came from the atmosphere and not buried dep

Because you should tax the thing you want to stop. Burning carbon is absolutely fine, provided the carbon originally came from the atmosphere and not buried deposits. It's the open-loop cycle that's the problem. The moment you dig it up, eventually it's bound for atmosphere. You want to financially encourage the development of "green" petroleum - nobody will bother if it's taxed all the same. Also, if you try and individually tax the hundreds of thousands of different uses for carbon, according to how much carbon each thing uses, inevitably you'll get it wrong, and this will create inefficiencies and perverse incentives to do arbitrage between the various poorly calibrated taxes. What you want is for the market to figure it all out!