Because it's unpopular, it also won't get discussed anywhere... ( My perception could obviously be wrong, bit it would get silenced immediately for bringing it up)
We have a powerfull union here in Belgium ( connections with politics) and since a lot had already accomplished, they keep fighting for ridiculous things for the mere purpose of keeping themselves relevant.
One of their most favorite is classifying teachers as very hard labor. Coming from a background where my dad worked 18/24 and 7/7 that stings. I know multiple teachers and I don't consider that hard labor. It's important labor, yes. But they don't have a lot of stress of other professions, not much working hours and a lot of vacation.
Keeping your course up to date every year is not stressful ( if that even happens. A lot of professors copy-paste their work)
Important note: depending on the students age they teach ( toddlers, middle aged, adults. I do believe it gets harder and they need to add more hours. But classifying everyone as one is a mistake in my POV.