Why remove items at all?
The Short answer, is that it makes room for new items.
Each item we add makes navigating the shop more complex. If we have 50 AP items, that is a lot of scrolling to find the one you are looking for.
We don't feel that having 2 magic vamp items is healthy for the game, in a world where Gunblade wasn't bad, seeing Akali with Gunblade and Riftmaker is a lot of healing for any champion.
As for Gunblade itself, we have wanted to remove it for a while. It has never been worth buying because its gameplay isn't particularly healthy either, easy burst+slow isn't great. Even if it was healthy, its duel AD+AP also gave it a VERY small champion pool.