10 health left, being chased by Caitlyn up river, near the dragon pit. Enemy jungler is trying to pincer her, so she can't reach the opening. She's gonna want to cross that wall. If she Qs, Cait can simply follow her and E. If she tries to use a basic attack; SURPRISE! Cait kills her(Really though, any ADC with 550 range can do that.) It's a situational example, sure, but it's there nonetheless.
Point is; Kalista's jump is only for positioning while in battle, and can't be used for much else. You can dodge skillshots with it, sure, but so can any other ADC by simply walking out of the way. There ARE some disadvantages to Kalista's jumps too. It's easy for beginner Kalista players to accidentally jump out of range, and even when you get a bit better at her that can happen sometimes. It's not precise, so there's a thing you can abuse against her. Another thing you can do is force her to constantly jump, that's actually going to lower her DPS that alone. While she's jumping, her attack speed is "capped" sort of. She has to stop and stand still to get her full DPS if her attack speed goes above what her jumps allow. And considering how people build her, that's gonna be about 90% of the time.