Why our grandpas were a teacher

In our ordinary conversation.. what were your grandpas doing? He was a principal, etc.. Oh, my grandpa was also a principal...

Between late 19c to several decades of early 20c this country had a lot of wars with foreign countries.
There are many cases the job of our grandpa was a teacher and sometimes a doctor. Because teachers were not conscripted, let alone a doctor. As a result they survived in homeland. That's why their off-springs flourished in current country.