Probably to make maps require less verticality for the mechanics they wanted. It'd be pretty hard to manage a camera angle at larger discrepancies for the same function. Either that or to make ranged builds more viable with major verticality in maps
It's also possible in 5e for a raging barbarian to fall an indeterminate distance at free fall and never die from it. You could orbital shock drop a gang of bugbears onto your opponent's military encampment from literal space, and every one of them would stand up ready to fight as long as they started the fall with greater than 60 hit points.
In short, 5e rules for falling damage are pretty silly and it's best to ignore or re-rule those if you expect to use it in any sort of sensible situation.