Almost everyone who cares does step 2, assuming they do anything at all. Very few people are qualified or bother to review source code, but everyone who performs step 2 can feel pretty safe, as long as a release is big enough that it's getting reviewed by experts.
So, what's the hardware equivalent? If I'm not capable of reviewing the schema of this hardware, but someone I trust says "this is great", how do I at least know the one I bought is identical to the one she/he bought (or built) and reviewed? How do I verify the components? This seems like a difficult problem.