In case of losing a device, all the data can be restored with these wonderful backups on the internet. That are not always encrypted. An attacker can attack such a service provider. In the case of public authorities, the service provider may be required by law to hand over unencrypted backups.
And it seems that soon this might be a moot point, as ghost stories seem to be developing, in which public authorities can force services to install a backdoor in the software or a state run MitM ghost protocol.