Why does Yasuo's ult not refresh like Zed's does?

So there have been several times where I'm playing Yasuo and I use my ult on someone, and boom, right as I hit R somebody else gets the kills, and I get full cooldown, which is my main problem. I don't have a problem with an assist, especially in a teamfight, but come on, full cooldown? What a waste of an ult. Didn't even do anything and now I've gotta wait a little over 90 seconds at most, but even at full build, maxed ult, 52 seconds is a lot to wait for if your last ult wasn't effective.

Why is it not like Zed's ult, where if the target is killed right after you use it, it automatically refreshes to zero? I think it should be