I am not able to understand what use is the manual antimalware scan? All antivirus software has a manual anti-malware scan. I understand if it's the first time someone installs it on their infected/unknown PC, the scan helps in detecting malware. But I can't understand in what situations are such scans useful when the antivirus software automatically protects machines in real-time?
Example: I purchase antivirus software and scan my PC for the first time with it, and no malware is found. The antivirus downloads updates automatically. In what scenario will I feel the need to manually "scan my PC for malware"? Can you give an example? If I ever needed to scan for malware, then why didn't the antivirus stop it in the first place? And if it couldn't identify and stop it in the first place, how can it be expected to identify the malware in the scan?