The level 70 crafted jewelry was really nice back in the day, as none of the non-crafted jewelry for DD and Healing jobs had any Vitality on it. By loading this crafted jewelry up with Vitality materia, you could really improve your survivability. When they added The Binding Coil of Bahamut - the first content in the game where Accuracy really started to become important - materia could be used to add additional Accuracy to pieces that didn't have it already.

Nowadays, though, there's no high-level crafted jewelry, and gimping your jewelry to level 70 just so you can attach Vitality may be more of a sacrifice than you'd be willing to make.