Rebooting is NOT a default action. But it may be necessary at times, eg when updates have been installed, or when something becomes completely stuck.
Our setup is such, that a user with physical access to the computer, can reboot it without needing sudo or other special powers. From the login screen, and from most desktop environments, it is possible to select an option to reboot (sometimes labeled
restart). also, it is possible to switch out of the graphical console using Control-Alt-F2, and then start the reboot using Control-Alt-Delete.
Yes, it is also possible to shut down a system. Please don't, under normal circumstances. It makes system management a lot harder. it also means that updates cannot be installed at night, so they need to be installed during the next working day, interfering with your work.