Alaska, I get your point. However, I think SailAK's is more fundamental than what you're describing. Sure, some here think it's crazy/foolhardy to leave the slip without being tied to a jackline while others, especially non-members, leave with all of the PFD's under the settee in the cabin. But the SailAK's example is more fundamental. How does one not know that the spinnaker halyard, which presumably had both ends free, isn't holding up the jib? I can understand that, on a new-to-him boat, the other guy may never have dropped the jib before and MAYBE he thought that the roller furler was keeping the jib up by itself, but this is a bit sad. It would be more analogous to a snow machine guy leaving without attaching the treads/tracks to his machine, and then insisting that it's supposed ot be that way.
I agree with what you are saying, that is why I started by noting that it was "quite the example" but my point was that it is not that uncommon to be shocked by what someone doesn't know. The PO of my boat didn't know that there was a locking bolt to hold the keel in place. Without it the boat can turtle if you get knocked down. To me this is essential safety stuff, but he had the boat for years and it just never came up. He had owned the boat and actively sailed it for years.
I guess I have just been noticing many threads lately where forum members are shocked at the lack of knowledge out there, and I am saying that we may be the harshest critics of all.
EDIT: And to carry on with the sled analogy, I think it is more like a rider having a sled for years that rides poorly, trenches, etc, and has never bothered to touch the obviously adjustable suspension that is covered in the incredibly basic manual. I saw this more often than not.
EDIT again: And also, did the owner get the information from the PO? There were a few things our PO showed us when we bought our boat that were directly contradicted when we read the manual, checked online etc. Had we not been the types that do lots of research we may have just continued doing it the same way. My favorite was when he showed me the bilge pump and it had been wired to a switch, under the dinette, that has to be held down continuously for the pump to operate. I know that that wont work in an emergency, but it had just never occured to him that it might be an issue.