Updates patch major security vulnerabilities. It’s cute that you think nuclear secrets existing in your hard drive are the only reason why you should care if your PC is infected with malware but it isn’t. Malware can steal your keystrokes, granting attackers access to your bank accounts and every other place you sign into online. Malware also uses background processes to do bad things, so your “multi-day” processes will take even longer when your computers resources are being hogged by nasty stuff.