S.R. Hadden (John Hurt) in "Contact": "First rule of government spending: Why buy one, when you can buy two at twice the price?"
Look again at my handle. There are plenty of times we needed one of something (special test cable/box) and had two or even three built just for the heck of it, because the "customer" was gladly paying for it. We always justified it as "Well, if the first goes bad, we don't have time to fix it, so this could keep the testing going..."
The best part is that the customer often doesn't know what they're paying for and lets the OEM keep all the stuff because it's not a contractual deliverable.
Defense industry: wasted time or wasted money. Take your pick (or both, should they cancel the whole contract early).