You don't have a swimming test before you go to the beach, and that's a deadlier place than a rock concert
What is an acceptable risk and what is an unacceptable risk? How do we mitigate some of those as much as possible?
Well, first of all the normal process is to identify the risk - one of the best risk assessments/management plans I ever did was when I asked the young people I was working with to do their own list of possible risks and hazards on a 2 day expedition. They highlighted cattle chasing them - not something that we ever thought of or included in our risk assessments as adults who had been in the outdoor education/activity sector for years, as well as coming from a rural background. Was that an outrageous one? No, in the UK cattle kill a couple of walkers a year so quite reasonable although unlikely. Likewise, in Australia the ABC released a bit the other week saying that cattle and horses were the biggest killers.
So based on that anecdote, if we look at how those are attending a festival or concert view the risks they are taking, what would they want to do to minimise their risks? They're going to do the party anyway, the drugs are part of that and what keeps them going for 14hrs+, so let's make it safer. If the government won't legalise the stuff, and therefore it's all made in a back room somewhere, let's make sure those people know what they're buying in the safest possible way.
People do different things to get their adrenaline highs - I tend to do something on my mountain bike or in the past whitewater kayaking and canoeing (which does also kill people), others do things involving driving fast/hard tracks etc - and this is just one of those things.
Most importantly, pill use is different to some of the other drug misuses, as it is not a daily habit - it's more likely to be a once in a while event, so the source can vary a lot... hence why testing is so important.