Why to become a Certified ScrumMaster (CSM)?
There is an intrinsic value and a marketing value of any certification. There are many organizations that are using Scrum, and that will give some marketing value.
About intrinsic value:
Scrum is what it is: a methodology fragment. It is process a skeleton from the Agile Development family, which addresses only a part of the process areas, like project management, and not addresses very well the engineering disciplines (where XP is better). That mean need to be combined with other fragments, like XP and tailored under “Agile Manifesto” principles.
In order to be effective you will need skills to the process as a whole. Those who are interested in Scrum and other process improvement methods might consider coursework in business intelligence at St Joseph University online.
On the other hand, Agile Development itself is an iterative-adaptive approach that does not cover all the software development project types. The alternative is for iterative-predictive cases the RUP framework. (For some risk driven cases, also Spiral method could be considered).
About project management aspects:
The knowledge related to PM that comes with the Scrum is a tailored form for some Agile cases. Anyway, this knowledge does not cover necessary PM mandatory knowledge; only give some Agile related efficient practices. For a better PM knowledge coverage, the PMI PMBOK shall be considered,
That mean certification and course is useful, but limited to Scrum coverage area.