It all depends on your installation method.
Some installers (e.g. Windows) include these files, while others (e.g. Ubuntu) do not, and even if you've used the Windows installer, you may have selected to skip the installation of the sample applications and tutorial files.
Another option is that you have more than one workspace folder on your machine, and you've switched form the default workspace which contained these files to another workspace. Note that the 2 common locations for the workspace folder are: 1. in the studio installation folder, and 2. your user home folder (in Windows this is the folder to which the %USERPROFILE% environment variable points).
See this thread for instructions on how to download the "missing" projects/files, and additional details on the workspace folder.
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