"Some of the things I like about Micropub media endpoints include:
• The spec allows the media endpoint to be on a completely separate domain from the "full" micropub endpoint.
• The spec doesn't specify anything about how the files are stored or their final URLs or filenames.
• They make it easy to separate the handling of (large) media files from the (presumably much smaller) content and metadata of a post.
• They enable Micropub clients to upload multiple files without creating multiple posts. This makes it simpler to create posts that contain multiple images, like a gallery."