And having your data always accessible without having to use the cloud or sync devices (did you forget to sync and now have conflicting versions?).
There's also having all your apps with you at all times and being able to access them without having to digg your laptop out (because that is so much fun on a crowded plane).
With a separate desktop + mobile phone, you can still use all the same apps on your mobile, and sync the data with your desktop - even remotely when needed. Also with a desktop you get much more storage space and CPU power, which you could use by remoting to your desktop with your phone over a secure connection.
Other than being completely wrong you are dead on.