Rudder trim is because propwash torque on the tail changes with speed, engine, and prop settings. Below a certain speed you need rudder to one side and above you need rudder to the other. They joked that Hartmann walked in circles because one leg was stronger from holding rudder at high speed.
The stabilizer is offset to make 0 rudder needed at cruise speed which helps reduce heaver low speed propwash torque, if you don't have rudder trim you get to move the pedals instead. If you do have trim then complain about that. Step on the ball instead.
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