While I agree that the amount cash one is carrying should be of no concern to the security checker, I think people are mistaken if they believe that it should be immune from having to go through the x-ray. At many airports, in the US certainly, the standard screening device for persons is a body scanner, not a metal-detecting arch. Going through the body scanner requires that everything be out of your pockets, including things like plastic combs, let alone wallets.
Thus, at these body scanners, you are required to put everything that you are carrying through the X-ray. This idea that you are entitled to get a receipt for your cash before putting it through the X-ray is impossible. Unfortunately, you just need to be trustful and observant, otherwise the entire system breaks down. And why should cash be any different from jewelry or other valuables? They often need to go through the X-ray, and nobody gives you a receipt for them. Rant over.