Wire gauge on Drones different?
The difference is in "rating", assuming higher responsibility and less liability in cases of automotive application (high temperatures etc.) as compared to drone application just for fun. Wires can withstand a lot of short term abuse before they evaporate. The drone application uses mostly open wires in high ambient air flow, while automotive wires are usually bundled and deeply enclosed. So the drone wires have better heat exchange with ambient, and therefore can carry higher ampacity. 

If you check the wire gauge table at Wikipedia, you will find out that a 3.3mm (AWG8) wire can hold 40 A with 60 deg.C temperature rise, and can hold about 470 A for 10 seconds before it overheats and destructs. So 120 A is possible for a short flight of a fun toy.