Most governments are bound by laws and regulations that effectively require waterfall development as every request has to be signed off before work can begin or

Most governments are bound by laws and regulations that effectively require waterfall development as every request has to be signed off before work can begin or money is dispersed. They also try to get the cheapest bidder in many cases. The entire industry knows this doesn't work, but there's no political will to fix it because it's easy to attack an opponent for spending money with no defined goal or for wearing anti corruption measures that drive a lot of the regulations that require defining everything up front