A: NPCs have names, backgrounds and motivations.
This week I was looking through the Keep on the Borderlands when I thought to myself "Hey, lazy ass. You need to finish fleshing out the inhabitants of the keep." Then it dawned on me that none of the inhabitants of the Caves of Chaos have much in the way of detail either. Dave Hargrave used to urge his readers to take a troll to lunch. That's a lot easier to do if instead of plain ol' "Troll (32 hp)" the DM is equiped with "Ignatz the Troll (32 hp), an excellent fisherman, a pariah among his kind because he actually gets more nutrition from the bounty of the sea than man-flesh. Willing to trade smoked herring for any wine or beer the party has on them. Seeks some sort of magical aid to assist in the wooing of a nearby mermaid".
Of course sometimes the players just want to slaughter nameless orcs. I'm not against that sort of thing. One of the great things about RPGs is that you can let your id go on a little romp and no one gets hurt. And I don't see why you can't have both approaches in the same campaign.