because it makes you unqualified to say that it's not a bloated sloppy mess. Because it is.
If the blogger just wants to write a blog and doesn't care about anything else, they can just use threads, or keep on using twitter, for that matter. But for some reason, this hypothetical blogger has decided that they don't want to use Twitter. They don't have to write their own static site generator, but in moving off Twitter, they're going to be exposed to some of the details behind the scene. If they're not an anti-intellectual, this hypothetical blogger can do some light reading to get up to speed.
You seem to think that the core of a microblogging platform is its software. Absolutely no. It's the community.
Again as I have already said, it's like requiring a blogger to write an elegant static site generator. Who cares that the Wordpress backend is messy and bloated? Only on HN will you find this fetish about an elegant backend when you are merely a user.