User blog comment:QuantumFeint/PBE ADC itemization/@comment-24474109-20140611145915/@comment-15244341-20140613235558

Since forever. Helps do more damage on an ADC than a BT. BT->Berserker's->Phantom Dancer->Last Whisper->IE->GA is pretty much as standard as it gets for a build for a class in LoL. Most of the "traditional" ADCs can do great with that.

Then you have the other less popular groups of ADCs which are the Blade ADCs (Trist, Kog, Twich, Vayne) and the Trinity Force ADCs (Lucian, Ez, Corki). All of these still buy IE.