Tomahawks are battle-tested - Flamingos are not. Ukraine can use all the help it can get, and a long-range cruise missile with a significant payload is basically the only thing that can destroy targets like drone factories. They can currently take out oil refineries and storage because the fuel is already there - the drones are just delivering the “fuse.” You can’t take out a drone factory with those same drones - at best you’ll damage roof tiles. Tomahawks would be a game changer.