It's funny, because I didn't remember this always being a thing...but that's I guess because it wasn't:
NFL hip-drop tackle in the NFL: Dangerous or necessary?Â* - Dawgs By Nature (see about halfway down)
It does seem dangerous. Of course, it's seemingly become popular because...players can't tackle in other ways which were deemed too dangerous.
edit: I guess it's been banned in at least one rugby league too:
https://www.totalrl.com/watch-unders...-rugby-league/