I seem to remember raising the health & safety question not long before I left a couple of years ago. The answer was that the legislation catered for exemptions for essential training.
I hated the CS trip as much as the next guy, but I realise why they do it. Most of pay lip service to this type of training, going through the motions. However, knowing that it will be nasty if you don't do it right in the first place, concentrates the mind.
As for building tents, etc, you'd be surprised at the ineptitude of those who'd never been taught how to do it. Given the demo/practice makes setting up a campsite a much slicker affair, especially when time is tight. I'm talking from practical experience - when it's pi**ing down in stair-rods, the guys who knew got into dry environment much quicker than the rest (well, would have done had they not immediately charged around helping the rest).