It's simply that the honour system sort of works, but the whole thing tips over when you introduce people who aren't honourable. This applies equally everywhere - I'd bet that if you tried this same experiment in the US, you'd have similar results. Some will be honourable, some will be unsure of what to do and give up, and some will take full advantage of it. I expect we'd see the same result with DRM-free movie downloads (except that the confused group wouldn't exist - they'd probably split with the majority going to the honourable side). A large number of people would go legit, and a large number of people would continue to pirate - or even pirate more.
(And the idiot thing refers to the fact that there was more than one self-checkout lane, and they all got locked up by alcohol purchasers, and this is even taking into account that it's illegal to sell alcohol on public holidays here - they should have known better, and they definitely should have got the message after the first one).