Malwarebytes Anti-Malware does not act as a real-time protection scanner for every file like anti-virus software so it is intended to be a supplement, not a substitute
Malwarebytes Anti-Malware is a complementary but essential program which detects and removes zero-day malware and "Malware in the Wild".
An anti-virus program alone does not provide comprehensive protection and cannot prevent, detect and remove all threats at any given time. Anti-virus and anti-malware programs each perform different tasks
as it relates to computer security and threat detection. Essentially, they look for and remove different types of malicious threats. However, there can be some overlap in functionality and detection features depending on the program's scanning engine, how the vendor defines a specific threat and what Naming Standards
Anti-virus software is inherently reactive
...meaning it usually finds malware after a computer has been infected. The security community is in a constant state of change as new infections appear and it takes time for them to be reported, samples collected, analyzed, and tested by anti-virus researchers before they can add a new threat to database definitions. Further, if you're dealing with zero-day malware
it's unlikely the anti-virus is going to detect anything.