User blog comment:Yordleportal/Essence Reaver theory/@comment-13709532-20140701220420/@comment-4022742-20140702174100

You don't have to, just like you don't have to build Statikk Shiv/Phantom Dancer/Trinity Force with an Infinity Edge. It just works better when you do, because; "synergy". When looking at the statisctics though, the lifesteal item is in the correct place as far as tiers go:
 * provides a fair bit of stats aimed at hybrid damage dealers (I really feel it's stats need to be lowered and have it's price dropped so it's more accessible)
 * provides the most AD and Lifesteal with a nice bit of resilliance passive
 * provides less AD and Lifesteal, but adds CDR and a Mana passive which is nice for casters
 * provides the least AD, but adds attack speed and a current health shred, I still consider it to be a counter item to health more then a core damaging item.

When looking at damage versus utility Essence Reaver fits in line with the other Lifesteal items quite well, the statistic of Cooldown with the Pasive mana gain is just too niche for it to be good on everyone.

Champions like Sivir, Ezreal and Graves will still have benifits with using Essence Reaver over BT or BotRK.