It's the writers' fault
Here's what I suggested last fall:
This show needs a drastic shift in direction
Here's a thought, why not make the zombies the real threat?
Gas has gone bad making vehicles useless, all while a pack of 30 million zombies from the north are tirelessly marching down on them
The group is forced to flee south and wind up in Florida, where they realize too late that the pack of 30 million zombies is going to trap them in South Florida
Eventually, they're forced to raft it to Cuba!
Why are the zombies heading south, you ask?
Because zombies are susceptible to freezing, so they instinctively seek out warmer climates