The problem with the RMD approach is that the withdrawal is a percentage of the current value of the portfolio, which can fluctuate wildly with market boom and bust cycles. During the Great Recession, it can result in one living on 60% in 2008 and 2009 than the amount in 2007. If one has enough discretionary expenses to cut, it can work. Else it is tough.
Hence, most people try to do a more constant WR method. Or if they withdraw more in a good year, they save part of it for future leaner years.
The nice thing about the RMD method is that it reminds us that we are not immortal. At my current age of 60, the life expectancy is 23. The RMD approach would have me withdraw 1/23 = 4.34%. That is not too far from the 4% rule of thumb.
PS. There are all kinds of life expectancy tables on the Web. Even the SS site has different ones for different purposes. It's confusing.
The number I quote above comes from the 1st page that a Web search found:
Life expectancy at 60 | Data | Global AgeWatch Index 2015.