Why Malwarebytes?

This topic really belongs in another board or subforum, but community.norton.com does not have a section for Other Products from Other Companies.

 

Why Malwarebytes?  This is not a Norton or Symantec product, yet several forum members discuss Malwarebytes for removing malwares.  Why is this necessary?  What is Norton not developing and designing functionality which Malwarebytes does?  Is Malwarebytes more advanced in some ways than Norton Internet Security and Norton 360?  If Malwarebytes can take care of some infectious problems that the Norton's do not, then is Norton in some way behind the trend in creating virus and malware definitions for definition updates?  Really, why are so many forum members here mentioning and using Malwarebytes instead of more strictly using NIS or N360 to catch and repair software infections?