Software Development:What, How or Why?

Many software development advisors address the topic of asking "What not How". Edsger Dijkstra showed in one of his early publications (197x ?) that "What" is just another level of abstraction compared to "How". On the next level every "What" becomes a "How". Therefore I think that this advise is misleading. It's needed to know the "What" and "How" on every level but to understand the requirements on any given level we have to ask "Why are these requirements specified?". Understanding the reasons may lead to a different design or allows to suggest alternative requirements suiting the goals better.