Isn't AMP considered an antifeature these days? Last I heard even Google had abandoned it — but this is outside my zone of expertise, so I might be wrong?
AMP for email is a bit different of a beast. It works a lot differently from the web version and is used essentially to add interactivity to the email. If you use Google Docs, it’s what allows you to directly reply to a comment in your inbox.
You maybe underestimating the number of people that use things without knowing what said things do, so those things just continue to live and never get migrated away from use.
