After some years of teaching Structural Geology, I have come to notice that most Geology students and scholars shy away from it. Is it because of its mathematical nature or what. Most geologists really don't fancy Mathematics as such.
This is true for other "hard" geology subjects, Paleontology, metamorphic rocks etc.. the tendancy is to follow new trends in rapid mutations using new tools, GIS, Remote sensing or more direct applied geology areas.
Geology students go where the jobs are. Where volcano's and earthquakes are offering lifetime careers there are people willing to take the jobs and do the math.
I am not a geologist but a Mathematician. I agree with Jerry that students go to the more marketable areas. For instance in Mathematics, students run away from Pure Mathematics to the more lucrative areas like Computer Science. Even within the Pure Mathematics discipline, students tend to run away from Abstract Algebra. Yet, these areas they are running away from are the basic and fundamental areas. For example pursuit of structural geology enhances the students' grasp of geology irrespective of the particular branch of specialty.