It's part of the general problem of the lack of stimulating material for talented students in any subject. It's not a popular priority for teachers, certainly

It's part of the general problem of the lack of stimulating material for talented students in any subject. It's not a popular priority for teachers, certainly less popular than remediation for low-performing students and measurable college-oriented "achievement" for high-performing students. Also, this is material that less than 1% (if that) of high school students will understand. Teachers don't bother with material that only one or two students in their honors class will enjoy.