And why are you asking for 160 to 4 when the next traffic is 20nm behind you and there is nobody in front or to depart????
In short,
A) Because its the "law"...or rather in its MATS 2 local operating instructions.
B) There may be nobody in front or behind you or no departures but you flying 160 to 4 means the tower know exactly how much time they have to do, for example, a runway inspection/cross a towing aircraft/route a VFR heli through the overhead etc etc etc.