Most software vendors are constantly working to improve their products. Operating System (OS) updates patch holes and fix problems. Anti-virus updates add new definitions and help your computer recognize, then deter, computer viruses. Regularly running updates significantly improves your computer's security and lowers your chances of having your system hacked. You can easily set your computer's default to automatically check for and run updates, so that you need not remember to do so manually.
Check out the post on macOS Sierra before updating your Apple operating system.
For more information on software updates and securing your computer, visit ITS Safe Computing.