I think OpenForce probably did this because calendar and file storage are each created on a their own pages in the user portal. When you manage applets from the control panel and add optional ones, there's no user interface for optionally creating a new page and putting the portlet the applet creates on that new page.
And the initial page structure's hardwired, of course. Having blank "calendar" and "file storage" pages would look weird!
Better would be more complete flexibility in the initial configuration but it appears we don't have that.
