Changes to Windows 10 have made it so that a regular shut down of your computer no longer functions as a "refresh" for Windows.
Restart is required to refresh windows, delete temporary files, and finish installing any Windows, app, device or driver updates required for optimum performance.
When should you restart your computer:
During Patch Week after updates (2nd Tuesday of every month)
Any time your computer or programs are running slow
Any time you are experiencing difficulty with functionality of apps or hardware (i.e. speakers or headphones sound "fuzzy", Outlook and office apps not working well, etc)
At least once a week!
Before you connect with any IT support professional for assistance - they'll likely make you restart again as well, but most issues can be resolved without assistance by restarting your computer