1. Humans work together
There are a lot of assholes in the world, but there are more normal people, which means that when a disaster or accident happens, more people try to help and collaborate than try to take advantage of the situation. We see this in hurricanes, tsunamis, earthquakes, car accidents and any other catastrophe. In a post-apocalyptic world, people would band together and collaborate; bandits and profiteers would be few, and established groups would not conflict with other groups, they would seek to collaborate as well.
2. Fights are lethal
Professional fighters are trained to punch people in the face with their fists, yet they often get injured and require specialized treatment and time to recover. You’re not a professional fighter and don’t have a team of doctors to treat you, you need to avoid getting hit as much as possible; without your hands, you’d die.
3. Feral dogs
Have you thought about what happened to Max and Bella? They most likely joined up with other dogs, forming a pack to scavenge for food from the wreckage. Over time, the dogs have reverted to a previous state, no longer man’s best friend, now they want to eat man. This has happened after events such as Hurricane Katrina and the earthquakes in Haiti. Before bandits and mutants, these packs would be an immediate danger to survivors.
4. Diseases and infections
Medicines last only a few months on the shelf before they spoil and lose their effects. The collapse of civilization means that there’s almost no one to produce new drugs, and any untreated injury could lead to death. Even during the first few months, when the drugs are still in good condition, who would know what substance and in what quantity you need to soothe those bruises that just won’t go away?
Rabies would be one of the most common diseases and one of the most constant and lethal dangers. Not only dogs transmit rabies, other animals that can transmit it to humans very easily are cats, cows, ferrets, goats and horses, as well as wild animals: bats, beavers, coyotes, foxes, monkeys, raccoons, skunks or groundhogs. Although it is not common, poultry can also be infected, but since they do not present symptoms, transmission from bird to human can be very easy.
Without an organized society, who produces food? Are you going to resort to hunting, fishing and gathering? Are you going to start a small vegetable garden? Do you know how to do it? Even if you manage to grow some potatoes and lettuce, will you be able to get enough iron? Vitamin B? Calcium? Chances are you’ll be weak and sleepy most of the time, that is if you haven’t gotten scurvy or leukemia. Engaging in a fist fight is not a realistic option.
Gasoline dissolves in a matter of days. After three months, and without a petrochemical industry to produce more, in three months the reserves will be depleted. Electric cars are not a more advantageous option either, without hydroelectric plants, who will produce the energy to power them? Solar cars might be a better option, but when damaged, will you be able to repair it, or even get the materials to try.
8. Cities would be flooded
In the absence of infrastructure and institutions in charge of urban maintenance, wastewater would no longer be pumped or directed to the sea and drainage systems would collapse. In addition, cities are not very porous to rainwater, as there are few areas of land compared to concrete or paved areas, so water would accumulate more quickly, covering some parts of the city.
Fires are common but usually do not become a big problem because there is always someone capable of controlling them. But even with government and infrastructure in place it is not uncommon for a fire to get out of control, without a competent authority, forests and cities would be reduced in a few years. Forests can grow back, but not cities.
10. Nuclear meltdown
More than 30 countries have nuclear power plants, and the number of these plants is more than 400. It is enough for just one nuclear plant to fail to produce an explosion so large that it would raise a cloud of radioactive dust that would cover the entire Earth. This would prevent sunlight from entering and consequently all plants would die. There would be lethal radiation all over the world, and only people living in underground shelters, where they could protect themselves from the excess radiation, would survive.