Customers often interact in amazingly creative ways to products and services rather than following your carefully designed plan. There can be unexpected results from various analytical tests, that may not be able to be explained with just numbers. By visually showing the process of what you think is happening, it helps share a hypothesis with others and shed light into what happened during a test. These insights can lead to new products or fundamental changes in your business model. The book Lean Startup by Eric Ries talks about this in length.
The framework for these is: This – Then That – Result.