They are neutral. They only get hostile when provoked.
And we already have a neutral mob, which becomes hostile when provoked and still doesn't drop anything. WOLVES.
But the majority of people find it more advantageous to tame wolves, and thus, it seems pointless to add a reward that no-one will get. Unless its something awesome, like diamonds. I'd kill my wolves for some extra compressed carbon:D
How come no one has said "A record"? Maybe they drop a record. Maybe just random items? How about they do not drop anything. Once you kill them, they copy slimes and turn into two smaller Endermen? Or maybe they turn into lava?
They're gonna drop 20 gold bars. These gold bars, when picked up, attract all Endermen in the area. The Endermen all join hands and jump in a circular motion around the player. When the volume is increased, there will be traces of a faint "no wifin' in the club, gimme twenty dollars, gimme twenty dollars" in the background.