Why is Google Scholar popular in some fields but not in others? In disciplines such as computer science and engineering, Google Scholar is a fundamental tool in not only searching for recent work of a researcher but is also frequently used as a metric for the proficiency of the researcher.

I've noticed in many other fields, e.g. political science, or even math, Google Scholar is not nearly as popular. 

Does anyone have any insight into why this is the case? Do these other fields have other tools they use to follow researchers or measure their output? Perhaps these factors are not as important in these other fields?
Math already has an excellent tool, MathSciNet.  And, more importantly, MathSciNet is much more accurate than Google Scholar.  

If you are a mathematician, look up yourself in both places and compare!