Ethics is what people agree on. Not doing unnecessary harm is usually easily agreed on. Don't exploit people who know less it's also on the list. Doesn't mean we didn't learn something valuable from KZ camp experiments, we just don't think it outweighed the costs. And we don't like, or want to encourage, people who think it did.

There are very strict rules for scientific experiments _because_ we know that without them, just guided by "common sense" or "be reasonable", someone would get blinded by ambition or "the potential" and go further than the majority want to accept.

Anyone can "experiment" without it being an accepted scientific experiment. But then they're personally responsible for any and all bad outcomes. If you follow the rules and get the experiment pre-approved, you'll likely be covered by your employer's insurance and free from criminal liability . That's a very good incentive.