DCThumb
The Army are the ones who are in direct contact with the enemy on the ground. Perhaps they are understandably reluctant to expose themselves to the consequences of being weakened by the interference of less qualified outsiders.
I repeat, it is the ownership of the capability and control of its budget that is critical. I cannot see the Army being happy about the RAF owning and funding Apache. Ditto for the RN with LRMPA. The colour of the crew is not critical. Command and control is.