That is a valid question, and while I’m nowhere near an expert on Mythic+ mechanics, I would say, it is to basically not trivialize the Mythic+ experience.
I remember, in expansions where Mythic+ was not in-game as of yet, after a few weeks of characters being at max level, and gearing up the Heroic dungeon experience, was less than… heroic, in my view. Eventually a patch would come along that would introduce a new dungeon, until the cycle would begin again.
I feel that this is not the case when it comes to Mythic+ dungeons. Higher Mythic+ dungeons are meant to be tough and challenging, and the mechanics should not be ignored or be simply out-geared. The participants have to find ways around them, be always on alert.
That is a very good discussion to have however, so please keep giving more
feedback on this subject!