Why do police officers use that fake monotone and deep voice they talk to you?

So that there is no hint of anything in their voice that could be used against them in a complaint. (e.g.: I'm simply furious that the officer talked down to me with a sarcastic tone of voice - he belittled me - he disrespected me - etc - etc - ad nauseum).

The tone of voice they use to give orders or instruction is known as a "command voice" and is widely used in both military and law enforcement situations when the speaker wishes to emphasize their Words and the intent he/she is trying to convey.

Some police officer think that fake deep voice "scares" people but to me it makes the officer look like an idiot.