Dashboards for things like banking websites can be complex; they need to show a lot of data in a way that’s easy for users to both understand and find what they’re looking for. To that end, it’s helpful to include sample data in a wireframe, to really demonstrate how the dashboard layout makes that data easy to understand.

That said, early wireframes for things like financial dashboards and other data-heavy sites can be more basic. An early version might simply show which sections will go where with data examples added in later versions.