I think you identified the use case: For services that are using the "append-only log as your source of data" then you need a tool that manages the "expensive

I think you identified the use case: For services that are using the "append-only log as your source of data" then you need a tool that manages the "expensive to reconstruct it" side of things. I think that is what this does: it materializes and abstracts interacting with the reconstructed view of the data.