that sounds interesting but can't find clear use cases

In fact it has lots of use cases,

1- For design tools, they can combine multipe images, texts, svgs and serve them with single pack/abstraction

2- When you need editable/composable images.

3- Future genai models for generating visuals/html/js/svg would have more feature rich abstraction/toolset

4- When you want to prevent base64 size overhead