Understood. I have been self-hosting WordPress for over a decade, so I have seen that it takes time for technologies to become mainstream, but I am also a technologist who is constantly learning. I want control over my platform. My current hosting provider provides the platform as a service starting as low as $5/month. FYI, newer platforms such as Micro.blog, support IndieWeb technologies (the actual specs) by default.
As for business case for using them, Chris Aldrich worked with his local newspaper to "IndieWebify" their website: https://boffosocko.com/2018/05/29/indieweb-ifying-coloradoboulevard-net/. He explains the business benefit to the newspaper.
For myself, I sometimes link my image posts to my Instagram posts. When people comment or like an image, the comments and likes appear on my website on the post I linked from. Example here: https://islandinthenet.com/historic-hightstown/
As long as you are logged into WordPress.com you can leave a comment on my website.