Why are rings unique equipped?

[Emerald_Wyvern]

I use 1 upgraded ring (180) and 1 non-upgraded one (170). But ofc some ppl run with 1 main stats ring and 1 off stats ring of ilvl 180,

And that's fine until you play a caster or a healer. We get one ring that we can upgrade and one non-upgraded until we get either a raid ring or something like the Garuda/Ramuh EX rings.