User blog comment:PurpleWii/The Evolution of the Tank archetype./@comment-6719710-20160425153717/@comment-1330314-20160429081902

But that's the point. Nobody wants to focus Rammus. Aside from his W, he deals very little damage, and aside from his Q, he has far too little disruption to matter. As you pointed out, there's no real incentive to focus him (in fact, there are plenty of incentives to not focus him), which is why he currently needs his taunt to function. Meanwhile, even an antiquated champion like incentivizes opponents to attack him with his debuffs and significant AoE. The core goal of a tank is to draw attention to themselves, but Rammus is the only one who really has to force enemies to attack him via hard game mechanics, which is why he'd probably not be a real tank (or a functional champion) without his taunt.