I am honestly curious. It seems like every item that competes with nashors anymore has ms, but nashors doesnt. Ludens, Lichbane, and most attack speed items have ms, and that ms is pretty critical for carries, but nashors does not have it.
MS would fit it perfectly, but it would need to be more expensive or nerfed other ways. It's a rare buy, but when it's bought it's quite strong.
Nashor's is one of those outdated items that doesn't really deserve to be.
I remember discussing this way back in the old forums about how odd it is that Nashor's is the one with CDR and Lich Bane has MS, when it would really be more beneficial for those stats to be switched.
If they lowered/removed the CDR, nobody would miss it. Fiendish should be replaced with Wisp, and Stinger could easily be replaced with Recurve in the recipe. Stinger is extremely outdated, having only 2 components despite how 4 of them could fit into its expensive recipe. It's cost could be lowered and we could give it a stronger AP scaling on the passive - because at the moment, the champions using it are extremely reliant on its power spike and that audience is currently extremely small.
Also, Nashor's isn't typically bought on carries. The three off the top of my head who use it to great effect are Kayle, Teemo, and Azir, and honestly, none of them really need the MS. Plus, Nashor's has the capacity to be a lot more lethal than any of the other AS items because the damage on hit is fluid and changes depending on your AP.
The items that build into it don't have MS on them. Luden's Echo and Lichbane build out of Aether Wisp and half the attack speed items build out of Zeal. These two items are just not part of Nashor's Tooth's recipe.
