Are these standards being relaxed because they were initially set overly cautiously tight, or are they being routinely relaxed without appropriate engineering?

Are these standards being relaxed because they were initially set overly cautiously tight, or are they being routinely relaxed without appropriate engineering? I think the problem is that no one really knows. No doubt the original standards were set with substantial safety factors. No doubt time and experience have given us a lot more data on what we can usually get away with. But the keyword there is "usually". However unlikely a major accident has been, it is getting more likely. And we won't know just how much more likely until it actually happens.