My guess is that it's just easier to find Calculus teachers vs Linear Algebra teachers. Maybe it's less obvious in the US but when I have visited schools in poo

My guess is that it's just easier to find Calculus teachers vs Linear Algebra teachers. Maybe it's less obvious in the US but when I have visited schools in poor countries you really get a sense of where knowledge in certain subjects tops out. I find people in the US seem to assume they can magically drum up a supply of linear algebra teachers, or the like. STEM teachers are technical professionals.