Hughes 500. Please understand that I am not seeking to defend it, ( It is the for the force to that) But the original reason is down to history. Devon & Cornwall were the first force outside London to experiment with the use of Helicopters. (81/82).
The force HQ was -& is at Middlemoor just east of Exeter. It was not realised then that an Air Support unit should not be used for the transport of senior officers, so it was natural that the new concept in Policing should be based at HQ.
I am not party to the reasons why it remains there to this day, but given the extensive examinations that all units have at regular intervals, I am sure that they will have their reasons.
Tigerfish