The fan kicks in if the motor temperature exceeds a certain limit. No denying that it is audible, though it is necessary to keep the fan on to ensure the motor remains at usable temperatures.
In case the motor is not cooled, the performance of the motor will have to be capped.
Usually, in cold weather, or under low load the fan will not turn on if the motor temperature is not exceeding the threshold.
Cars usually have much bigger motors that can radiate more heat owing to the fact that they have more surface area and material usage, and, noise Insulation for a car cabin is super easy compared to an open 2-wheeler. Something that makes cars seem quieter.
Also, most electric cars have liquid cooling, which is quite difficult to include in scooters from a cost and space perspective.