Because screw classes or specs that dual wield or need a main hand and an off-hand like a shield, right? You’re already limiting the gear drops to once a week at the highest we can do, why make gearing any more difficult especially when this should be seen as extra catchup gear alongside the nightfall events.
It’s not like the void-touched gear has amazingly powerful procs or effects that would warrant a unique tag anyways.
No, its there for a reason.
Whats the reason? The gear isn’t insanely powerful so what could the reason POSSIBLY be?
The gear is so insanely powerful it needs to be limited
What would that change?
except the mace for outlaw, which even at 658 is a better choice than anything else in keys 
While I absolutely feel you in terms of how bad it looks with it being unique equip… The good news is that once you equip the void-Touch gear, it unlocks the upgrade track for the tier below without need crests.
I am a PvP, I don’t do dungeons or delves or raids, so Crests tend to be at a premium overall… I completed 5 mask run, unlocked Hero-track weapon. Purchased my 1H and then equipped it. Went to upgrade NPC and found that because I had the 1 hero track weapon, I could upgrade my 2 PvP conquest weapons (champion track) all the way to 8/8… which is also item level 658… without using any crests.
So there is a built-in ilvl catch up. It isn’t necessarily perfect, but its actually kind of genius.
Aside from PvP, you can also get a zero-effort Champion weapon from the Nightfall weekly quest. Just pick up the quest, sit around waiting for the event to finish, and tag the boss before it dies. Ezpz.