Ashe pays for her utility by having 0 mobility.
Kalista pays for her utility by having.... infinite dash, health % percent damage, a ult who can be both use to initiate or save a person 100% of the times, infinite scaling damage. While ashe has a slow, a skillshot stun that doesn't last that long if you don't hit it from afar and....... that useless passive. There is no reason at all to play ashe if kalista exists.