The difference is that if you host with an actual hosting company, you can move your content if/when you grow dissatisfied with it and lose no traffic or rankin

The difference is that if you host with an actual hosting company, you can move your content if/when you grow dissatisfied with it and lose no traffic or rankings. If you're on something like Facebook, YouTube or Medium and don't have a custom domain... well you're just screwed if things don't work out.