It will soon be possible to discard more of the in-box apps that ship with Windows 10.
Currently, a handful of pre-installed apps can be removed, including OneNote, Skype, and Weather, but most of the other built-in apps are permanent fixtures. Windows 10 has also promoted a number of third-party applications such as Candy Crush Saga to the chagrin of many. These don't appear to be going away, but such apps have always been uninstallable if you don't want them. However, the latest preview build of Windows 10, build 18262, enables the removal of apps such as Mail, Calendar, Movies & TV, and the Groove Music app.
The ability to remove these apps doesn't really mean much in terms of disk space or convenience, as none of them are very big. The move may be of more interest to corporate deployments; an organization that has standardized on Outlook, for example, might want to remove the Mail and Calendar apps to reduce user confusion.