I suppose the example is poor, then. Food chemist are pretty much trained to do a rather narrow range of jobs, pretty much all called something with "food chemist". A mathematician (and most other academic degrees[1]) isn't really trained to do any particular job at all (except research, I suppose), so they need to cast a wide net. A better example might be a "Java Programmer" not even considering looking at job postings in the .NET section?

1: Plenty of vocational training takes place at universities and have degree-titles attached to them. That doesn't make them academic pursuits. I say this as a polytech-rebranded-as-"university"-trained engineer and I firmly believe that I shouldn't hold a degree that implies that I have an academic education.