What are you talking about? New assets? The game is a couple of months out of release, these are from the original assets. Ergo, why are they limited to multiplayer in a single-player based game? Why can't the Inquisitor, someone of incredible influence and power who has access to resources all over Thedas, get the armour of the Arishok when a Katari mercenary (who is vilified by the Qun btw) can? It makes no sense. All of the armour the Inquisitor gets looks boring and samey. Great game and all, but I just despair when I see some no-name noble wearing incredibly detailed (and sensible) armour. I'm just stood over here in my trench-coat that for some reason can defend against all manner of weapon. Finally, take a look at the concept art. Look at how many different armours they had planned for the Inquisitor, some of them even helmets that match each set. Are we to believe that they ran out of time and had to ship with the armours we now have? More likely that EA is going to bleed our loyalty dry again and make us pay for them.
You anti-multiplayer types don't do logic very well do you? Multiplayer has its own independent development team working on content. The multiplayer team created those armors, not the single player team. If you want to know why the single player team didn't take those armors to use in single player, your question has already been answered, because they're only designed to fit one specific race and gender. Its many times easier to create unique armors when you only have to develop it for a single body type.
DAI has as much armor variation as DAO and DA2, 90% of the armor in both of those games was just recolors of same small handful of armors, with a few unique armors sprinkled in, and I can guarantee you that both DAO and DA2 had dozens upon dozens of armor concepts that never made it into the game... just like DAI.
In the end, if you don't like armor designs in the single player game, give some constructive criticism to the devs, instead of throwing a tantrum like a spoiled child because you think someone else got a slightly shinier toy than you.