I don't know about common sense. If you are a regular boater, there are things that are plain and obvious to you..common sense if you like... but are actually learned behaviours.
Modern cruisers with their microwaves, telly, and ensuites look and feel more safe and domestic than different and boat-like. Everything works at a button press and if you are not mooring up, (that is challenging to beginners) life seems easy. My point is that some people may be lulled into a false sense of security and relax their vigilance? The Wear It campaign does seem to be working though, there are lots more LJs in evidence than there were.