These rules had not been reviewed in 30 years, and clearly since that time, two key factors have changed. The first is longevity. People are living much, much longer. Second, rates of return in today's environment bear no resemblance to the rates of return in the early 1990s. The issue is, very simply, that at the current withdrawal rates under the old withdrawal schedule, people were going to run out of money. This change will allow them to retain a certain level of funds and income for the remainder of their life.
On May 28th, 2015. See this statement in context.