I found with WizTree that there are some apps in C:\Program Files\WindowsApps that seem not to be installed for my user, and I'm the only user on my computer. Examples are games like Candy Crush and Disney Magic Kingdoms. I found a solution to uninstall them in the following thread.

Basically, you have to start PowerShell as administrator and run the following command:

Get-AppxPackage -allusers  *disney* | Select Name, PackageFullName
Get-AppxPackage -allusers  *disney* | Remove-AppxPackage -allusers

The first command lists all apps that contain the string disney in their name. The second command removes all apps that contain the string disney in their name. You can also use *candy* to remove Candy Crush and so on.