A few reasons. The US was very corrupt back before the Progressive Era and to clean that up in a hurry we got a bunch of very prescriptive rules around procure

A few reasons. The US was very corrupt back before the Progressive Era and to clean that up in a hurry we got a bunch of very prescriptive rules around procurement that prevent the use of common sense and make bidding for government contracts a hard to master skill that reduces competition. We have a federal structure and use a common law framework so the interaction of law, precedent, and agency rules create a confusing thicket of regulation that's hard to deal with. Finally, outsourcing of planning to consultants means frequent shifts in direction and makes it harder to exercise control over costs.