"Honesty Bar"

While in vacations at the beautiful island of Madeira (I truly recommend it), I was amazed by the pools' bar management philosophy. It was called the "Honesty Bar" and it had no waiters! Besides that it had everything else a normal pool bar can have: fresh drinks, all sorts of snacks, chocolates and candies, bread, cheesse and ham that you can use to make a toast. It had also the several devices used in similar bars such as a coffee machine, ice refrigerator, and a toaster. Most impressively, it had a small safe-deposit box with a considerable amount of money, which you should use to pay for your consumption (all the items had a price indication) and do the changes yourself. At the same time, you should also indicate in a sheet of paper what was your consumption, how much did you pay, and what was your appartment number. Did it work? I would say I don't know for how long does it last, but by the amount of money there was in the box when I payed for my cheese and ham toast and "Brisa Maracujá" (passion fruit drink typical from Madeira), and a considerably filled sheet of paper, it worked perfectly!!
The question is, why did it worked? Or why would it not work in another context? Is it the vacation mode? The fair transaction happening between the turist and the appartments village? The fact that it was occuring within a small community of turists?
I think answering these questions would be an interesting exercise to understand the puzzle between altruistic and egoistic economic behavior.