Because it's fine the way it is. Red Death is a hard counter to it. Both are 2-shot kills, but the Red Death heal cancels out the Thorn poison, so the Red Death user comes out on top. Hawkmoon has a faster TTK with the 2-shot, and is [i]far[/i] more accurate at range. Body shots do more damage than Thorn body shots do, so it's less punishing if you miss. MIDA takes a steamy dump on Thorn at long range (not surprising; it's a Scout Rifle, long range is their thing). The Last Word and the Vex are the kings of close range. If you can't kill a Thorn user up close with em, you aren't playing correctly. Sounds harsh, but true. Thorn is a powerful weapon in team engagements, where the poison can keep the enemy on the defensive constantly. At that, it excels. At any other role, other weapons will outshine it. The reason we see so much Thorn hatred is that the gun is very easy to do "decent" with. The poison ensures that even mediocre players will pose [i]some[/i] threat. But does that mean it should be nerfed? At high level play, Thorn is by no means king. So should the gun be nerfed out of the top-range tier just because it's such a menace in random matchmade Crucible? I sure as hell don't think so. And this is coming from someone who would use a Red Death, or hell even Hawkmoon, long before I'd use a Thorn.