Restoring backups

I’ve noticed that you can import posts from various different types of blogs, simply by logging in. But, we can’t restore a blog hosted on https://www.wordpress.com without having to go through the rather complex and time consuming procedure of, effectively, restoring the database manually. I’ve also noticed that wordpress.com allows us to import wordpress backups and to backup the databse in few touches of a button. To my mind, this doesn’t quite make sense.