It's not the implausibility that's worth noting; it's that it implies something about the world which only terrible people believe. Let me give you an example:
There's a moment in Season 3 in which some of the main characters are driving along in their product placement SUV and a random, able-bodied survivor in a backpack tries to flag them down, begging to join them.
They pass the guy, ignoring him, the unspoken understanding being that they can't take on another mouth to feed. Later, at the end of the episode, they pass by the same dude, now lying dead on the street. They stop, take the supplies off his dead body, and drive off into the distance. The message is clear: In this new, dog-eat-dog world, all people are good for are the food and tools in their backpack.
So ... what if it had turned out that guy was himself a badass zombie-killing machine? That'd come in pretty useful, right? Well, maybe they could tell by looking at him that wasn't the case (no visible weapons, not covered in enough zombie blood). Fine. But what if he turned out to be a skilled surgeon? Or an electrician? Or an expert gardener? Or a carpenter? Or a mechanic? You don't think they'll ever need somebody who can heal wounds, or hook up a generator, or grow food, or build a shelter, or repair a vehicle? Really? Because it seems like 90 percent of the group's problems could be solved by somebody who knows what the hell they're doing.