It is largely due to how gold-efficient support itemization can be.
Ivern doesn't need a jungle item (sitting on Hunter's Talisman mostly of experience), so he can just build utility items and CDR. As a result, he can become rather difficult to kill very quickly while providing a lot of utility for his team.
There is very little you can do to stop him from just walking into your jungle and stealing buff camps whenever he has Smite up. His durability, CC and quick clear (channel + Smite) kills it very quickly. Generally, you will only get one of your buff camps unless you manage to steal one of his.
In addition, his passive lets himself and another ally get any buffs he clears. This means that his allied laners can always have the buffs from his second clear on.