If you use Facebook as your blogging platform, the dollars generated by showing ads to your audience go to Zuckerberg.
If you host your own Wordpress install, the ad dollars go to you.
If you're Mark Zuckerberg, bloggers blogging on Facebook is better than bloggers blogging elsewhere. That's the circumstance under which blogging on Facebook is better.
While I tend to agree with this exact comment (since it's Facebook specifically), I don't agree in spirit because administering your own Wordpress install takes time. That time might be valuable for some.
I'd certainly run my own Wordpress, but not everybody wants to.
If you host your own Wordpress install, the ad dollars go to you.
If you're Mark Zuckerberg, bloggers blogging on Facebook is better than bloggers blogging elsewhere. That's the circumstance under which blogging on Facebook is better.