Distinguished professors write college-level textbooks. When I took AP history we used Morrison & Commager’s two-volume Rise of the American Republic. It opened my eyes to all the ludicrous simplifications and chauvinism in my high school texts and gave me a love of history that lead to my being a historian.
And that’s why distinguished professors don’t usually write high school-level textbooks. They don’t want to go through the process that makes textbooks acceptable to school boards, nor do they have to.
There’s also far more prestige to writing college texts. And the money is probably greater. True, a state or city buys a lot of textbooks. But they also keep the same ones year after year and colleges can require every class to buy them. Paul Samuelson’s Economics textbook made him literal millions.