It becomes a bit of a slippery slope when you start to seperate the ninja daggers from each other, and while I would love to do the look of a short sword in my main hand with a dagger in my off hand while playing as a ninja, I also realize that once you do this for ninjas, then you also open the door to monks wanting two different fist weapons equipped, red mages wanting to mix up their jewel and rapier, bards wanting different arrows for their bows etc etc.

This creates the requirement of a lot of work for little in-game benefit, and while I always do think more options are better, I also would say that if implementing those options takes away other meaningful, playable content, then they should place it on the back burner.