You gotta know what liability is like in the USA. Of course they have to do this.
You don't need to be afraid of US style litigation to be concerned about divers exceeding their limits and training on your watch.
Heck, if I were responsible for a club outing and one of the freshly minted members wanted to go to 25-30m (80-100ft), I'd have a serious chat with him, strongly discourage it and suggest an alternative dive plan. I'm in no danger of being sued, but someone getting bent or dying on a club outing kinda ruins the mood. Not to mention the bad press we'd get.
The liability issue depends on whether a dive centre would be negligent in the event of an accident. In order to be liable, three things must be demonstrated:
- The dive centre owed you a duty of care
- The dive centre failed in that duty of care
- somebody suffered a loss or an injury
This is the basis of tort law in most jurisdictions in the western world. A lot of cases never make it as far as the courts though, and often businesses or their insurers will pay out early doors as it is cheaper than defending the claim. The USA does have a reputation for everybody bringing frivolous lawsuits, but the rest of the world isn't far behind.
Over here, I have only been asked for a cert card once. It was at Porthkerris divers which is a camp site by the beach where they allow you to shore dive or get on one of their two boats. They are a PADI dive centre, so they are probably following their standards rather than complying with any legal requirement. Elswhere, there are boats operating from Scapa Flow, Anglessey, Oban, Lochaline, Seahouses, Portsmouth, Ilfracombe etcetera, and not one will ask for proof of qualification. Many will ask you to sign a form saying you agree you have participated in a safety briefing and that you are suitably qualified and fit to dive, but they don't give a toss what that qualification is.
The reason for this is, specifying a qualification can often cause more harm than good. We have all seen divers with all the cards in the world who we feel shouldn't even have a PADI Seal Team card. Owners of dive boats do not want to be in the position where they are in court explaining why they deemed a particular customer as suitably qualified for a particular dive. They are in the business of getting you to the site safely and recovering you from the water - once you're off his boat, he has no control of what you do in the water so the diver makes the call as to whether they can undertake the dive.
A dive centre in Malta who we use regularly always check cards and officially will not take you beyond the limit of your qualification. The difference there is they are providing guided diving, so they have a duty of care to their staff. For that reason, they need to do some sort of check before letting them get in the water because they don't want to put their staff in a position where they have to deal with a problem diver. There is still some risk this may happen, but when you are explaining to a court how you try to ensure safe diving practices, it will be extremely difficult explaining to a judge and jury (who are probably not divers) that what you were doing was safe when the incident occurred at 30m and the diver had a bit of plastic saying they were only qualified to 18m.