It doesn’t answer the question fully though. You’re basically saying “because”
Generally speaking, jewelery is defined by its gems (in particular crafted) and that extends to named items (I think all, or maybe not?) When the slot is empty, you can obviously slot whatever you like into it but I believe that is then fixed? Empty slots for jewelery didn’t even exist in initially, they were added to somewhat reduce the abysmal issue of lacking jewelery drops in loot tables (“old ring”, oh the quality content we get). Initially, you couldn’t even slot a gem into those
So they fixed that.
It is inconsistent, though. The OP has a point. I personaly think the whole gem system in this game is just nonsense. And it was made way worse with casings. I think they should be permanent and you should be able, with the stonecutting skill, to switch the gem out from a casing but retain the casing until you decide to replace that.
Edit: if you go on NWDB and look up a jewelry piece, then it says whether or not you can replace the gem. I do not know what decides whether or not you can replace the gem Maybe pre-Brimstone vs post-Brimstone jewelry?
He was just making that up, a lot of named jewelry has exchangeable slots. Pieces like the “illegal” thrust/keen ring wouldn’t be BiS without it.
However, to @STAR33’s initial point, it’s extremely inconsistent. Some named jewelry can be swapped, some can’t. Some post-Brimstone jewelry is exchangeable, others aren’t.
yeah that too why we cant change gems on crafted jewel … you really think a gem is gonna change economy balance !! that’s some high iQ thinking there !! can you explain why or how it gonna affect economy?