But despite your cynicism about "any gov't regulation body", you would agree that professional associations have by and large been a success in protecting the public in areas like construction trades, engineering, law, and medicine?

Not necessarily. Recently, Miami condo collapes. In the not too distant past London building fire. I'm sure if we were to go looking, we could find more examples. Are these edge cases?

I have less experience with other trades, but you did call out construction separately. My family comes from construction backgrounds at various levels. The 80s in the US saw a boom in the 20 story building construction, and then saw a total collapse (no pun intended) in the construction industry. There are lots and lots of building contracts won by lowest bidder, and the only way to do that is cutting corners somewhere. Usually in quality of material, or reducing the "over-engineered" portions to the point of risking saftey, etc.

It's also widely known in construction that the permitting offices can be gamed. Talk to the right people with the write phrases. NYC is infamous in that people playing by the rules get absolutely nowhere. You have to start spending cash and using influence to get things done. It's all just pointless to being corrupt.

Interesting. I would see the occasional failure as actually a further indication that the system is working— that it's maintaining a balance wherein most practice is within the bounds of what is safe, but it's not NASA-level lockdown where there's massive waste due to unnecessary redundancy and safety factors.