Why is it good?
1) Prevent Stealing
Admit it, it will happen, you will kill a mob and someone is going to take your loot, even maybe a card!
2) Promoves Diversity of Characters.
Most popular chaaracters for grinding are the ones who can AOE (Knight, Wizard), there is another aproach to grinding; single fast killing character (Assassin, Hunter) but withou autoloot those characters are not viable enought therefore less people are going to play those clases.
3) Server Atractiveness UP!!
This will add even more to the list of cool features Ragna0 alredy poses, because if we want something that is more players!