The point of visualizations is to communicate and present data quickly and relevantly, while maintaining the accuracy of what is being displayed. Visualizations can be created and then added to the Master Item list with predefined dimensions and measures.
The predefined dimensions and measures can be Master Items themselves.
Sitting in front of a blank canvas on top of an unknown data model can be overwhelming for new self-service users. It is therefore beneficial to create some standard (and usually the most relevant) visualizations as Master Items so that the business users can quickly drag and drop them on their sheet to create their bespoke dashboard.
It will significantly improve the self-service experience. Inserted Master Items can always be unlinked from the asset panel and provide the user with a starting point in modifying an existing visualization, including all of its settings, as well as dimensions and measures (instead of beginning from scratch).