I don't know how/when states started eliminating inspections. when I started driving in NY, inspections were a big deal, emissions too.
I think a simple federal guideline would be good, and here's why: back in '95 I got a neat old '83 F-100 from my father in law in Louisiana. valid inspection, all legal (they call the inspection sticker a 'brake tag', cause if your brakes work, you pass!)
I moved to Virginia, had to get it re-inspected, and all kinds of things failed, kingpins, parking brake, tires, etc. spent like $400 to get it to pass.
only 8 months later, we moved to Pennsylvania, had to get it inspected again, and had a whole NEW list of things failing!
emissions, rust, etc. so I just cut my losses and sold it.
used to be also in PA in one zip code you needed an emissions sticker, and the next zip over you didn't (as if pollution doesn't travel...)
point being, why is something that's 'safe' in one area of the country 'not safe' somewhere else?