Should come from your base sector and drop in your base sector? What do you even need the plane for then? It gives no chance to shoot it down. The difference is that luftwaffe deploys it in the map so the plane can be shot down and even the resources may be captured by allies. Allied drop comes from enemy base to your base so if it deploys fuel it cant be taken by axis. It also doesnt need fuel sector to be used.
Almost all maps have some kind of safe fuel (+sometimes even ammo) point for each side. If you control no fuel point, the game is pretty much done for you, even the Allied Fuel Drop couldn't help you there. So the arguments of "you need control over a fuel point!" and "but the enemy can steal it!" are quite weak, if not even invalid.
The conversion rate is another ridiculous thing. You pay 100mun for 30 (mostly) fuel as ally. Meanwhile, Luftwaffe supply gets 50 fuel or 150 ammo for 200mp(you can even get fuel
OR ammo). Manpower income is also about 4-6x higher than ammo income.
So, while axis are happily converting 200mp into 50 fuel or 150ammo, the allies have to pay 100mun for 30 fuel with a high risk for AA guns rendering the 100 ammo wasted and the doctrin as partly countered.