Perhaps because the long boats fit such a surprising number of passengers, making the life-jacket-to-person ratio quickly tend towards zero.
Incidentally, don't you hate it when you're having a nice and peaceful time, enjoying dinner or a sunset, and someone asks you "Is everything ok? You look so sad." There is just no good answer. Perhaps I should say "I wasn't sad until you accused me of it, but now I am because the moment is ruined." But what I actually say is something like "No, I'm not sad." (Original, eh?) However, you just cannot say that without sounding defensive (or, perhaps, being defensive), which merely exaccerbates the dilemma. On top of that, if someone then twists the knife with "Are you sure?" It's like "Yes, goddamnit, I'm sure I'm not sad. Now shut up and let me watch this frickin' sunset."
No, I did not ask her if she was sad. Indeed, it's hard to imagine how anyone could be in less than a sublime state when heading back to the pristine beaches of Krabi peninsula.