I just read the reason for this is that if you are accelerating hard, the car would drone very loudly, which is not the sound one would expect from hard acceler

I just read the reason for this is that if you are accelerating hard, the car would drone very loudly, which is not the sound one would expect from hard acceleration. You would feel the acceleration, while the default noise would sound like you are at a steady pace. By imitating gears, the steady drone is mitigated to some degree, and you won't be tricked into thinking you are not accelerating.