I see people refueling at the marina and public dock all the time without
regard to these basic precautions

Some of us don't have our boats within 10 miles of a marina. We need another
way to get fuel to the boat. Loading it up on the trailer and taking it up to
the shop-n-rob isn't an option either.
Certainly fueling from cans in a marina is frowned upon but the lack of body
count from the millions of boaters who fill from plastic cans in their back
yard seems to make this look more like a marketing or insurance decision.