How come fuel is rarely a major target? According to AH gameplay, the more fuel that is destroyed, the less they can up with. My question is, if every canister of fuel is bombed at an airfield, the enemy should have no fuel available to even takeoff, correct? Why are all other targets bombed first and fuel is rarely touched? 
Because it doesn't work like you think.
When you destroy half of the fuel tanks, the enemy loses the ability to carry drop tank. If you destroy them all, maximum fuel allowed is 75%. Which is, in most situations, too little of a gain to make it a worthwhile target.
A long time ago, it used to be 50%, but this in turn had too much of an impact, so it was changed. Porking fuel is one of the game mechanics that's difficult to set 'right'.
