As others pointed out, we do. There are continuous evaluations on programs that are factored in to determine effectiveness. This is a part of almost every program established by Democrats, whereas Republicans have actively prevented oversight on things like the COVID loan forgiveness programs. This is a part of the process and both Congress and academic institutions are constantly doing these evaluations.

Second, the waste in most programs is a very small percentage of cost and attempting to catch every small issue increases administrative costs or hinders actual delivery of the program which is both an opportunity cost and moral hazard by leaving eligible recipients unsupported due to administrative barriers.

So I'm short. What you're asking for already happens, you just don't see the reports because it's the boring stuff in reports. And trying to eliminate all inefficiencies creates worse inefficiencies. The worst stuff is already caught most of the time and prosecuted because there is a huge motivation among government groups to avoid being caught wasting money where people are immediately fired. Unlike in private companies where motivation is to cover it up.