On the one hand, taking combat away for 2 days/month forces people do do something else, even if that is nothing at all. It makes people try to find another activity. If there was something captivating enough happening in MD, players might focus towards it in those 2 days.
This already exists deep within the wish-shop. I'd dare say too deep, but that's not for me to decide.
Lore-wise, if my memory serves me right, DoT was meant to be dedicated to realm-wide Night, which never happened. Again, it's been a long time so take it with a pinch of salt or correct me.
So it serves a