because its a feature...




.. of gear design. gears adds noise, gear to gear contact adds more noise.
if u ever driven a manual car, u'd know reverse gear have much louder whining. thats because it adds extra gear for reverse rotation.

take example of recent grinders (lagom, weber, turin, etc). they are quiter since they all have direct drive motor. altho they do have a different issue of stalling instead, their main point of noise is just the burr shape and beans grinding, with only more powerful motor being louder.