Except it is? Instead of cramming 22 new features, 198 bug fixes, and 3 usage changes in the next version, taking 24 months of dev time, one could release the next version with 1 new feature and however many bug fixes fit in the time frame, and release it in 4 to 6 weeks
And you avoid making an app that you show to the customer for the first time only for them to say, "What the hell is this?" My company used waterfall for the longest time, and this happened several times. It was really frustrating.
I convinced my managers to move away from waterfall to a more iterative process using a financial analogy. Pretty much everyone understands the concept of compound interest as it applies to both debt and savings.
I framed the release of small but functional components as the equivalent of small, regular deposits to a retirement account, where benefits start to accrue immediately and then build upon each other with every "deposit". I framed the holding off of a major project until completion as the accumulation of debt with no payment plan. I also pointed out that, like a sound investment strategy, the "portfolio" of features might require adjustment over time in order to meet objectives under changing circumstances, adding substantial risk to any monolithic project.