[crazygringo]

It's to avoid the very specific form of corruption via kickbacks, essentially -- and if you look at the history of how politicians used to spend money in the US, you'll see that it is actually quite effective at this, and that it was once a gigantic problem -- and continues to be in some countries today.

You're right that it does nothing about other forms of influence like the revolving door.

And like I said, it comes at a tremendous cost of efficiency and quality. It's not trying to strike a balance between corruption and efficiency/quality, it's trying to explicitly minimize corruption at the expense of efficiency/quality.