It's not just drones, occasional specialist aircraft or museum pieces that make a comeback from the Boneyard. ISTR that large numbers of A-10s were brought back into service from there post-GW1 when the USAF realised that it was actually a very useful aircraft. The Boneyard gives the US the ability to 'hibernate' capability in a meaningful way - without the finality of turning aircraft into razor blades before the ink dries on a decision to retire them!