Separation of powers.
1) Legislative: decides on major and not so major issues, passes laws - hopefully after due deliberation - in the USA, Congress
2) Executive: implements laws and decisions made by the legislative power - in the USA, on a federal level - the President and his/her cabinet
3) Judicial: sees to it that laws are abided by
To make any decisions, information is needed for all three powers. Institutions like GAO, DOT&E and many others provide that information. To cut off the flow of information because it slows down the executive power may seem opportune in the short run. In the long run it will lead to nasty, costly surprises(*), not to mention the decay of democracy. If applied to developing heavy equipment and/or weapons, lethal surprises. My father had bad things to say about inadequate equipment he was sent into war with. He returned minus some friends and one leg, plus physical pain that lasted for the rest of his life.
Simplifying the world may make life easier, but not always better.
<edit> (*) - Well, lots more of them. No matter what you do, there will always be some nasty surprises. To do away with feedback in any system simply insures it will grind to a halt quickly - if it doesn't explode first.
<edit 2> Is DOT&E doing a good job? I think so. Congress sets new targets (possibly after some convincing - if convincing fails, no new target), DOT&E judges performance against them. If you don't like the targets, take it up with Congress.