[nshepperd]

Seems to me this is a principle-agent problem, really. Manufacturers and the FDA are only liable for one part of the system's safety - immediate injury or death attributable directly to a specific error. They're not liable for the gradual systemic damage caused by not using closed loop algorithms (due to worse blood glucose control).

Hence hobbyists home brewing this stuff. Only when you're making things for yourself are incentives properly aligned.