I have to disagree slightly here. While yes it's hard, unexciting and hard to measure, that still isn't why organizations don't do it.
The reality is that it just takes an incredible amount of time. This is especially true for startups and companies trying to move fast. You have to ask yourself — should I spend 2 sprints talking with customers about their problems, or 2 sprints building a POC that I can then test directly with them. In most cases, good PMs, engineers and designers have some basic idea for a solution that usually gets you 50% of the way there. So while I agree with the article is spirit, it's not a one size fits all process.