Why are traffic stop police always concerned with how "mellow" i am?
Well it sounds as though you already know the answer to your "do I need to signal" question. But just in case - YES you do. Even if you are completely alone in the dead of night, no one else around you are SUPPOSED to signal your intentions to turn. Stupid as it sounds, that is the proper way to drive. AS for your "mellow" question - officers expect a certain amount of anxiety when they flash the lights, bump the siren and pull you over. They are trained to look for "abnormal" behavior and normal for a traffic stop for most people is typically a) nervous cause they are normally law abiding and don't know why the cops pulled them over or b) angry that they are being pulled over. Abnormal behavior would be you - mega mellow. No anxiety might mean drugs or drinking. Other abnormal behavior would be too anxious, twitchy, etc might also mean drug use or something to hide.
It doesn't matter if you are in a "turn only" lane or not. The law in most states requires you to signal before making a turn, and there is no exception made for being in a marked turn lane. SInce you said you were pulled over at night, but didn't say how late, the officer might have reasonably believed you might be under the influence of alcohol or drugs based on the fact that you seemed too relaxed. Late at night, there are more people leaving parties and bars, so it is more likely that someone might be intoxicated at that time.
Are you required to signal in a turn only lane? Of course you are. Out of courtesy for other drivers who don't actually know if you really intend on turning.
They usually ask me if I am 'nervous;' I think that is a trick to make me nervous.
They're called pretext stops. Anything to initiate an investigation. Their on a fishing trip, don't take the bait
They know you will soon cause an accident because of your constant drug usage.