As an advanced controller, too often people switch to ground before exiting the runway to request taxi to parking. This makes it impossible for us to issue an exit or back taxi command. Never switch to ground until you have pulled past the hold short line! A couple examples as to why:
Airports with multiple runways:
Often, an exit command involves crossing, or holding short of a runway. This reduces the workload of controllers as we do not have to go to ground to say the same thing. It also reduces the risk of a runway incursion by the aircraft inadvertently crossing a runway without permission.
Airports with a backtaxi:
EGLC is probably the best example for this scenario. After landing on 09, you must pull of to the side of 27. The only way for us to get you to parking, is to issue a backtaxi command. If you switch to ground, we have to tell you to switch back to tower, often wasting the small window that we have, causing more delays for everyone.
So please, for everyone’s sake: stay on the tower frequency until you are past the hold short line and ready to taxi to parking.