[The Colonel]

I'm guessing that in most heroic fantasy, dogs make for quite a dull enemy. In a realistic setting, they are a lot more dangerous than a lot of people give them credit for (and surprisingly hard to shoot).

I suspect computer games tend to neglect them as it's hard to make the human opponents dumb enough to support the stealth mechanics without having to introduce dogs that might as well be deaf and anosmic. Although there are definitely dogs in the Fallout Games and Deus Ex had them in at least one mission.