My experience is pretty dated but back when I did some work with DARPA retention was a mess at the two defense companies I interacted with. Management wanted to minimize getting security clearance for employees since it involved a substantial amount of money/effort to get and then it was almost guaranteed that the employee would immediately jump ship to another better paying job requiring clearance elsewhere.

The other disturbing trend I learned about was how even if a company lost a contract, they would almost inevitably still work on it as a subcontractor for whoever the new contractor was. Part of that makes sense but it gave me the impression that no one ever really loses a contract.