The motorcycle fuel tank is relatively small, and the pressure of the tanker is relatively high, so it is easy for gasoline to overflow when refueling. The engine of the motorcycle is just below the fuel tank. When gasoline overflows, the engine that has just stalled can easily ignite the spilled gasoline and cause a fire. And when the motorcycle starts, there will be some sparks from the exhaust pipe. Once you encounter the accumulated oil and gas, it is easy to cause the gas station to catch fire and explode!
Everything is for security reasons.