User blog comment:Rapacious/Rapacious's sexy guide to understanding ranged AD builds/@comment-3450702-20120201192248/@comment-3238314-20120202142654

In my honest opinion, I think the pros like Last Whisper better because it's cheap, its components are cheap and don't require idling too much gold, and the penetration is available to you from the first hit, and on skills.

But this by no means that it's a bad item, it's just not popular, You can see pros getting it in dream hack, if it makes a difference:)