The user wants to quickly understand the general shape of the dataset used by the system, the extent of it, and what patterns might exist within it.
The system provides an attractive visualization that takes all the underlying data or a subset of it, and renders it into an easily comprehendible visual. This may be a static image or, if interactive, it may form part of a Dataset Explorer.
In general, users struggle to understand what it means when data powers a system, especially when the reality is that that data is just a list of abstract variables. Using a visualization to illustrate the nature of that data is an incredibly effective tool for helping users build a mental model of the system. In contrast to the Dataset Explorer pattern, where users want to understand and validate the data on a granular level, here even if that visualization is a big picture simplification or only portrays a small subset of data, it can still be a very valuable asset to share.