Is there are reason there are unnamed unique passives on gold income items (jungle and support items)? Since they are unnamed they only don't stack with themselves and since you're limited to one gold income item, you could never get duplicates of those items, right?
I'm not entirely sure what you are asking honestly, so I'll try my best to discern.
Many of the gold generating items Unique Passive is that they are "Gold Income Items". As such, you may only purchase ONE "Gold Income Item", as specified on those items' tooltips. However, there are gold generating items that can be purchased alongside "Gold Income Items" such as Avarice Blade.
Most of the stats aren't Unique Passives (CDR, etc.)
Unique Passive is generally used in one of two ways:
As far as naming them, it's for one wide reason: It's a mechanic that's tied together. When you see Conservation on Ancient Golem and Elder Lizard, you know they're a very similar mechanic (Identical, actually). Same for all the Chalice upgrades. For similar reasons, you can't stack them. This also helps sell item progression on things like Spellthief's Edge -> Frostfang -> Frost Queen's Claim.
So it's more for consistency's and theming's sake than strict game rules, since you couldn't stack them anyway.
