@Serapheem: I think the best answer is the Armed Forces have been heavily engaged in battles all over the nation. A significant percentage of troops have been lost, or — far worse — turned and converted. So, most of the good stuff has been used up already. There are few reserves that have been kept away from all contact, and they have the gear that they have. Let’s assume the Reapers have been used, are deployed elsewhere, or their crews have been converted.