Gems: Unique vs Unique-equipped

Is there any reason (other that oversight) that all gems are not Unique-equipped instead of Unique? It's pretty frustrating to have to replace your cool, unique gem with a trash gem so that you're able to pick up another one to put in upgrade gear (if you want to keep the old item still).

I cannot think of any harm to the game by changing all Unique gems to Unique-equipped, and I can think of a lot of benefits. Thoughts from the community?