There is no need to be connected to the Internet all the time to work. Although chrome machines usually are not so powerful and they can't be used for tasks needing high computing (such as code compilation, data processing) but Crouton at least allows to work (like coding, version controlling local copies with git) completely offline.

Crouton allows for the use to alt+tab back and forth from ChromeOS to Ubuntu seamlessly. No rebooting the device, no logging out.