The ability to prove the origin of something over "Source: dude trust me bro" is critical to a great number of people.
But sure, let's stick with "yeah nah, this piece of paper says what's in the box is in the box so it must be legit" because FOSS is gonna get salty about this.
You can hear plenty about the use of xrays (and how unwieldy that is) to verify electronic circuits in some CCC videos. I commented about some of the challenges of false negatives in another version of this thread (which was strangely posted three times by MIT? Is reposting daily until you get traction acceptable behaviour - may have to try it myself some time :)