Because there's always a trade-off between robustness and usefulness, and it's not at all obvious the FDA hits the right balance, especially given the extremely

Because there's always a trade-off between robustness and usefulness, and it's not at all obvious the FDA hits the right balance, especially given the extremely asymmetric incentives they face. If they approve a drug that kills a bunch of people, the repercussions are bad, but if millions die while waiting for a drug to undergo a decade of testing, the FDA isn't blamed. http://marginalrevolution.com/marginalrevolution/2015/08/is-the-fda-too-conservative-or-too-aggressive.html http://marginalrevolution.com/marginalrevolution/2015/08/is-...