It's also driven partly by a preference for that kind of regulation from the companies themselves (though they would prefer less regulation overall). Having to follow a bunch of rules on FDA trials is a manageable, mostly predictable expense; large, nearly unlimited potential liability if a drug turns out to have significant negative effects 10 years down the line is much scarier to managers and stockholders.
That's one reason the health industry is currently lobbying to move it in exactly the opposite direction of what you propose: they want less broad liability, and are willing to accept more FDA micromanagement in return if that's what it takes. The proposed bargain is something like: the FDA should tell us what to do, and if we follow their rules, we should be shielded from all liability.
Regulation = Barriers-to-Entry. Businesses accept (and secretly cheer on regulators.) People get this connection, even though it is non-intuitive on the face of it.
What is less studied are the regulators themselves. They rarely impose the kind of regulation that opens industry actions to sunshine and converts them to common knowledge.
There is a substantial body of theory that shows that the price system breaks down in the face of informational asymmetry. But regulators don't go for it since it does not make them more powerful. That's human nature. And it's fine with businesses, who would prefer to answer to the One rather than the Many. Preserves barriers to entry.
That's one reason the health industry is currently lobbying to move it in exactly the opposite direction of what you propose: they want less broad liability, and are willing to accept more FDA micromanagement in return if that's what it takes. The proposed bargain is something like: the FDA should tell us what to do, and if we follow their rules, we should be shielded from all liability.