Why is there a lack of sophisticated UX, usability, and UI discipline in the current design of safety-critical apps and devices?

A friend of mine, a User Interaction (UI)/User Experience (UX) designer and a usability expert that is doing some work at a technology-based medical device client, wrote to me wondering why many medical device companies don’t have much of a UX/UI and usability focused discipline in their marketing and product design teams. The simple reason is that many device manufacturers are still following top-down monolithic processes like waterfall instead of more agile processes that allow feedback-driven requirements definition.
Source: The Healthcare IT Guy - Category: Information Technology Source Type: blogs