Sure, but there's something about just logging in via SSH to a server and sending your post in one command. GH pages is easy to set up, but it's not 'hey it's all done for me' easy.

No matter what you do, GH pages requires more complexity and setup. And that's not a bad thing in this case, it gives you flexibility, but I can see a lot of people preferring prose.sh simply because they don't care about making a website, they just want a blog.