Maybe it's easier to kill someone when they're asleep.
Snoozers can kill though. In MO, right before the Poop Chute, I killed all those Interns with the Snoozer. It took ages though. You see, the darts just put them to sleep, but the electric shock thing actually injurs them. I just kept doing that until they were all dead!
Anyway, if snoozers are in an army with sligs...I'm sure they could've just installed nasty weapons on them.
-oddguy