I wonder why Riot can't make Tenacity effect displacements?

Have it reduce the time you're airborne after being knocked up.

Have it reduce the distance on knock-back abilities so you're not thrown the full range.

Stuff like that seems simple enough, I mean you have abilities in the game that get extended range on their displacements based on level after all. So how hard is it to allow a stat like Tenacity to reduce them back down?