You can blame college professors. (And I have been one.) High school English classes (and math, and history, and science) are structured according to the skills and content necessary for academic pursuit at the university level. This is why we study Shakespeare in high school and not Stephen King, and why we read classic works of fiction rather than classic works of, say, philosophy. Classic fiction created the modern English Professor. And no other field depends so much on the old texts.
If high school English classes were driven by business, or journalism, or medicine, or politics , or advertising— or just about anything else, really — they’d be very different, both in reading selection and the skills asked. (Few literary essays, for example.)
But the same actually applies to math and history and even the sciences. Biology would be a very different class if nurses drove the content, to take one example, but the same applies to geology if taught by a materials engineer or national park service marshal.