If a lot of guns were blowing up, I could see your point. But they aren't. So what you're buying with your proof laws is exposing your gun to unsafe pressures to prove it will take these unsafe pressures, which is no guarantee it will, after being stressed, continue to be safe. I don't see the logic behind that, but if you're happy with the false sense of confidence it gives you, so be it.

P.S. A lot of our laws also predate government my centuries: The Ten Commandments, for example.