I expect it would be another one of those things that maybe could have been done if they'd had the idea when they were building the game, but with the current system there's no way to add in such information now to make an item slowly change appearance with wear.

If such a thing was included from the start though, I think it could have been useful to link it to the 'gear condition' stat! (If your gear is looking worn, it's time for a trip to the repairman....) Or have three setting options of [on] / [linked to status] / [off] so you can opt to have it look like that for actual wear indication or just for aesthetics.

If I ever design an MMORPG, I'll keep it in mind...