Why Operation Deadlight sank surrendered U-boats

Why was Operation Deadlight carried out instead of using the surrendered German submarines?

Most were worn, obsolete, badly built, or troublesome to scrap, leaving little reason to integrate them into Allied fleets.

The surrendered submarines offered little fleet value after hard war service, obsolete technology, and declining late-war construction standards. Their worn and increasingly poor-quality equipment made them unattractive additions to Allied fleets that already had their own submarine programmes. Scrapping the fleet also raised disputes over which country would receive the material, where the work would occur, and who would pay for it. Contaminated and toxic materials made dismantling particularly unattractive, to the point that even the Soviet Union showed little enthusiasm for the job. Sinking the boats became the simplest disposal answer to assets whose recovery value did not justify the logistical trouble.