I don't understand Akali's W

I know it's getting a rework, but still, I personally think the slow that comes with it is pointless and just plain annoying. It has nothing to do with her kit. Lets be honest, I have never seen an Akali manage to get a kill because of the slow from her W.

ACTIVE: Akali throws down a smoke cover which lasts for 8 seconds, granting sight of the target area and slowing all units within it.

First off, how does smoke make a person run slower? This really bothered me ever since I got Akali and read her abilities. Also, wouldn't it be cool if instead of Akali being completely stealthed while inside of her smoke shrowd anyone that enters it will be able to see her, but instead they won't be able to see anything outside of the shrowd?

I just thought it would be a cool alternative instead of just making her invisible and slowing you. (And vision but most Akali players don't know what that is kappa pls no downvote)

Of course it will probably cause some balance issues that I am not aware of, but I just thought it would be neat if the smoke could blind people like Quinn and Graves can.