conservatism (in the form of : the kids would never learn how to write properly if they don't time their strokes with dipping the pen in the ink routine)
They started with ink, it worked for them, so we obviously also had to.
For me it was even worse. My teachers argued that I must not use my Pelikan pen (all my classmates were on fountain pens) and write with pencil instead, because I was using to much force.
The most infuriating thing about it: I never saw a teacher using anything else than a regular pen. Strictly forbidden. Those were for grown ups.