Plans form the base of a Route and cannot be published. The second stage involves turning this Plan into a Route, which you can then publish if you want. As soon as a Route is created from a Plan, the Plan is deleted.
The advantage of this two-step process is that it provides you with a useful and quick overview of where you are in the development of the route. You can also use this feature to create a simple interim plan when you are out and about and then edit it later in detail to create a Route that you can then publish.