I believe that the new ways of doing math are primarily there so people with PhDs in math education can write papers of dubious quality about them and new textbooks can be published. Without the new techniques, the old books can serve until they fall apart and new editions need only be published to remove dated references every couple of decades (what’s a record and why do I need to calculate how many times it would spin in five minutes?)
“PhDs in math education”
You NAILED it. For you others, these are people with ‘EDUCATION’ Degrees, not MATH DEGREES, but they get to pose as ‘experts in math’ and they are the ones who write the textbooks that prevent your kids from learning math. REAL Math Majors would NEVER write this garbage as they’re as disgusted by it as actual parent are.