It's the perennial tradeoff: do you want reach or ownership. Of course, you want both, but getting reach from your own site takes effort, time or money (or all three). Platforms like Twitter, etc, allow you to leverage their reach, but then take ownership of the content (at least the form of content you put on their site, which may include excerpts or links or user click data).
Like they can't add IPFS or dapp code to any of these?
I recently deleted some things on medium that I wrote years ago and had zero trouble doing it. Try that in some arrangement where you really grant ‘ownership’. “Hello Microsoft, would you please remove the background animation from the BSOD”.
What is really more of a technical detail, the domain name of the site serving some content, seems to take on outsized importance for some people. As far as I can tell, this are not actual creators of content of the sort where it would start being lucrative to swindle them out of ownership.
Case in point: AMP. If Google had, from the beginning, made it possible for AMP content to be served from the publisher’s (sub)domain, opposition on HN would have likely been half as fierce, or less. As we now know with some certainty, AMP really was a ploy to screw over the competition. It’s quite excellent that it failed, but it did so mostly due to people falsely believing they are getting screwed over due to this implementation detail, when really it was competing ad networks who were getting the wrong end of the stick, but wouldn’t have been in any position to stop it except anti-trust litigation.