The rules do not need to be followed precisely, if it is not possible within the game engine (see the point I made about Cover) or the addition or removal adds to the overall spirit of a D&D game.
Providing Advantage, for free, with no cost and always on, simply for being above your target breaks *over 56 other features*. 56. 56 balanced implementations of Advantage or Disadvantage, rendered useless because of that change.
That does not make sense nor is it fun to play, because the game turns into a repetition of King of the Hill each and every single fight with any verticality, at all. Having one tactic be the overwhelming "best option" in ever single scenario is not, to me, tactically interesting. It is downright boring and repetitive.
But I digress. Because it invalidates *at least* 56 other class features, actions, and spells. That is unacceptable for game balance.