The biggest reason IMO, would be for the gold enchantments vs. purple enchantments in addition to the base stat differences.
@Potenza Except that it's not the difference between full gold and full purple. The jewelry will only ever affect 3 pieces of a set, and in that, the difference is often minor compared to the cost.People say the difference is very small - it is when you look at only one piece that is gold and you compare it to its purple counterpart. BUT if you campare two full characters - One in complete purple items and one in complete gold items - you will see a BIG difference in power and resources.