Why didn't Riot just make Duskblade melee only?

I would've been fine with how it was if they had made it melee only. The new one is also fine, don't really care much, except for the fact that I have to ban Vayne every time if I want to have a fun game that doesn't involve me getting one shot. So why not make it melee only? It was obviously intended for primary role assassins not Vayne to abuse it.

Heck, while you're at it, make Sterak's and Iceborne melee only too.