Part of the problem is that while the math doesn’t change, the approach to teaching it does.
Every decade or so there’s a new broom as the new administration fumbles to “fix” education. Recently it’s been NCLB followed by ESSA. Meanwhile there are also trends and fads in education research, which trickle down to the classroom through teacher prep programs and administrators who need to look innovative in order to keep their jobs.
Not all of this is bad! If your old methods aren’t working (they’re not), it’s worth trying new ones. But it does mean that even in math you’re never going to get an “ultimate” textbook.
Every decade or so there’s a new broom as the new administration fumbles to “fix” education. Recently it’s been NCLB followed by ESSA. Meanwhile there are also trends and fads in education research, which trickle down to the classroom through teacher prep programs and administrators who need to look innovative in order to keep their jobs.
Not all of this is bad! If your old methods aren’t working (they’re not), it’s worth trying new ones. But it does mean that even in math you’re never going to get an “ultimate” textbook.