Elise's Rappel

It there a reason why Elise's Rappel doesn't allow her to travel to allies or allied units? Her cooldown for the ability is much higher than Katarina's blink, which can target allied and enemies and do damage, and Jax's damaging dash and Lee Sin's Shield Dash (although those two have costs). It makes her escapes very conditional and sometimes impossible. I understand that it's a move that makes her untargetable and has larger range but the range could easily be decreased 50 units for allied use and kept the same for enemies, and Fizz's 3rd ability allows him to be untargetable, traverse 800 units, and still allows him to deal area damage at a maxed base cooldown of 8.