Why JSF is not so popular as MVC framework like Spring MVC, even though its older?

Answer 1

• There are many implementations of JSF like Mojarra, Primefaces,
  Richfaces etc which makes it difficult for the user to comprehend
  learn and adapt to whereas Spring MVC has only one implementation
  maintained by a Single group of developers which avoids confusion.
• Spring has got great integration with data management through
  standalone or ORM frameworks out of the box which is lacking in JSF
  based implementation.
• DI and IOC design patterns makes it very easy to integrate existing
  legacy applications with new Spring based applications whereas JSF
  does not have such kind of capabilities.
• JSF is a component based framework whereas Spring is a
  Request-Response based framework and hence easy to understand and
  relates closely to MVC, Struts2 and other similar frameworks