I think it had to do with the fact both "worlds" rarely, if not never, interacted with one another.
Printable View
Also, I had a thought...
SPOILER AHEAD!
What if Urianger is the Warrior of Darkness?
I mean, he met with Elidibus at the end.
Necro-threading because of Shadowbringers >w>
I could get into the WoD thing... If the Ascians didn't always present themselves as mustache twirling evil villains throughout the entire series. Hard to get on board with people like that.
Just because we are going to be Warriors of Darkness doesn't necessarily mean we'll be working with the Ascians, I actually very much doubt we will.
He only wants to kill us because we're 'shining too bright,' which as we've seen, can threaten to return the world to the Void. His goal is to bring Zodiark back, but his main goal is to keep the balance of light and dark.
https://i.imgur.com/HnnAuOL.png
Note: "Her emissary" is Minfillia. This cutscene is after Hydaelyn sends her off to prevent the First from becoming a Void.