Another major factor that goes unmentioned is the tendency of the legal requirements to establish a threshold that people meet, but rarely exceed, as you note. It's understandable, you go to the effort of learning the legal requirements and meeting them, no small matter, and afterwards feel like you're "safe". The boat wasn't required to have connected smoke detectors because it was "grandfathered" in, and so the owners feel like it's not really necessary. There's no law covering whether my residential house has to have connected smoke detectors, and I decided not to, based on the idea that I would be woken up by any smoke detector in the house, and that every room has an alternate immediate exit to the outside, even if that means I might break a leg. But when you're talking a three-story boat, with a large number of people, and necessarily limited egress, might not the owners decide on their own, "Hey, the crew on the top deck might not hear an alarm from below decks, better hook up the smoke detectors"? You see that all the time. There's a legal minimum for the width of a bathroom stall. Smart people say, OK, I'll build to the legal minimum, and realize their elbows are bumping the sides because the legal minimum is ridiculously tiny in practice.
I'd like to see a points-based system that would allow for tradeoffs. The roving watch is worth a lot of points, but you don't have to have one if you have centralized water ingress and non-toxic automatic fire suppression systems in every compartment that are tested monthly. At least that would make the owners think about what scenarios they're trying to mitigate, rather than checking boxes on a list of legal minimums and calling it a day.
