Banshes veil

I Guess this item is now becoming the item everyone builds. I have yet to understand why riot has made it an AP item? mages already do extreme damage and now they are even harder to kill? makes very little sense to me. Especially after they nerfed the Rylai's Crystal Scepter because it was the go to for everyone? so why make another item be the same? [slayer-jinx-unamused]