Well, it is connected to the nose wheel steering and doesn't just "trail" as you put it. It is hyd powered by the Centre Hyd sys.
To quote FCOM 1:--
"Main gear aft axle steering is powered by the center hydraulic system.
Main gear aft axle steering automatically operates when the nose wheel steering angle exceeds 13 degrees to reduce tire scrubbing."
So, it's like 4 wheel steering on a Honda, it is an active part of the operation and doesn't simply "trail" like a stupid dog!!