Aside from being quest givers (or kill targets), loot holders, canned comment makers and general world furniture, mobs and NPCs also sometimes act as role models for players.
“I want what he’s got”/ “I want to be able to do what he does” is one of the most powerful motivators in gaming. And in MMOs, we aren’t just modelling ourselves on more hardcore players – no, that’s an old MMO model which encouraged hardcore guys with their amazing flaming swords and sparkly mounts to hang out in capital cities, that has largely been discarded in favour of letting everyone have shinies (possibly at a price). We’re also getting our ideas about what we want for our characters from the NPCs.
Does anyone else think, “I wish I could do that!” when they see an NPC use a particularly cool ability (why can’t MY shield breathe cones of fire??). Or “I wish I could have that armour (why can’t I have a cool set of deathguard plate?).
Various games have experimented with letting mobs drop copies of gear they are wearing or using. Players, I think, have always enjoyed being able to visually link some loot to the boss which dropped it. In pen and paper games, it’s pretty much de rigeur and players would be shocked if a) the NPC declined to use some useful item in its possession during a fight and b) if said useful item was not lootable afterwards.
But we’ve been moving away from these sorts of virtual world/ immersion arrangements with loot, where mobs drop something which would be logical for them to own. I think it’s a shame. I always liked the idea of looting a characteristic weapon or armour piece from a particularly tough enemy. And as for the dream of being able to spew fire from my shield like the second boss in Grim Batol … who knows, maybe next expansion …