Nintendogs taught us the valuable lesson: if you don’t feed your puppy, it won’t die… or age… or poop, it just drops magic pellets and whines. It’s not as if you could expect anything else from Nintendo… this isn’t a Tamagotchi, after all. If it was, we could beat our puppies when ever they misbehaved.
As far as the death aspect, how disturbing would it be to cut your game on and see a dead puppy surrounded with flies on your screen? Granted it might be fun to toss a frisbee at it, but that would get old after a couple hours or so.
Side note, Dueling Analogs is now available for download on your iPod at Clickwheel.com. Check it out as well as the other webcomics you can download.