There is no easy way to automatically add a widget to every product within a specific category.
Every time a new product is added, you have to go and edit the widget and add this new product to the list. Which becomes a problem when we are talking about 1000 of products.
The use case for this is a product type where we want a global instruction text for all these products within a specific category.
We do not want to include this text in every single product description, because we want to update it centrally on one location if needed.