> "pre-approved vendor lists" or "streamlined approvals" and that sounds great in principle, but could also easily be exploited.

Nearly any kind of public spending can be exploited, including auctions. There are countless cases where the cheapest vendor that satisfies the written criteria is chosen, only to end up with delays, cost overruns that far outweigh the initial savings, or equipment that malfunctions and breaks.

I know somebody who was in charge of writing these auctions for their government department. They picked a vendor, and then worked backwards to write the requirements so that only that vendor would satisfy them. Not because of corruption, but because they knew that vendor's equipment was quality.

There was another case, in a different department, where this was not done - the auction was written naively (and honestly), and the cheapest vendor chosen. The equipment failed within months, putting people at risk, and a different vendor had to be quickly chosen.

It's better to just put some conflict-of-interest guards in place, and then trust the judgment of whoever needs those goods, than to try to eliminate corruption through bureaucratic procedures. Because it can't be eliminated with bureaucracy - but efficiency can, and will be.