I have not seen the movie, but I have read the book, which I think explains a little better why they don’t stay at the nicely stocked shelter:
The man is clearly dying, and needs to get the boy to the coast before he dies.
And, what, was it the End of Days? 
For what they called a blizzard (maybe a 1/4 inch, non-accumulating), half the plant I was looking at shut down and the news people were telling people to stay indoors.
Yeah it was a lot like The Road, actually. The grocery stores were raided, the power went out, and people began to eye their neighbors hungrily. 
As I have said in many many other threads, including this one, this is a fatal and stupid flaw of many post-apocalypse movies, which seem to be operating from a pretty silly stereotype of “survivalists” as necessarily being of marauding bandits or selfish hoarders who do nothing but prey on other people, and the hero is inevitably a lone-wolf character, one man against the odds, fighting it out for himself. Nobody ever bands together in these movies except to do something evil. The Postman is the lone exception to this and it demonstrates that in reality, community organization, fortification, and defense would be necessary in an “SHTF” scenario of extreme severity. Why? For the obvious reason: strength in numbers.
If something like that happened and everyone in my town was not annihilated, the first thing I would do would be to find everyone I know or am on friendly terms with and arrange a meeting. We would take an assessment of all of our things: our cars and trucks, our guns, our stockpiles of food, and the various skills that we all possess, and then come up with some kind of plan for how to stick together and, if travel were not a necessity (to avoid radiation or something,) retreat to an easily guarded area and set up fortifications, camps, trailers, and the like. Sounds complicated, but it could be arranged with a few phone calls to the right people and a convincing speech about how the only way to survive is to stick together. (If phone lines are down, it could be harder - I’d have to actually go find them - but still do-able in this small town.
Fuck the lone-wolf thing - I’m not going it alone. I will do my damndest to get a group together, preferably composed of people I know and trust.
I get your point about it happening too quickly (I’m actually working on a project right now that plays with that concept) but at this point its been about 10 years. I think its safe to say in a world with completely dwindling supplies- basic human decency and stick-fucking-to-it-ive-ness would fall a part by then.
The much maligned/applauded film “Testament” does this well. Right after the bombs the town comes together- has meetings, pools supplies, etc but after a few weeks and the supplies running low and people getting sicker and sicker everyone retreats back to their core families for survival.
And at some point, even families will fall apart. Are you going to feed your kids or your parents? Your brother who knows how to hunt or your sister who’s whining that there’s no pizza?
Brian Aldiss called this type of scenario a “cozy catastrophe.” It’s a pretty common sci-fi trope. Your vision would get you on the shortlist for first to be eaten.
What I liked about The Road is that it ignores this kind of lemonade out of lemons idealism you’re describing. When you can’t grow food, when you can’t hunt animals for food and where law & order cannot be enforced, do you really think your utopia will band together and collectively decide to starve to death? Not that I think armegeddon is coming any time soon but I do think McCarthy’s line of thinking is far more realistic than yours.
Just saw this yesterday, and it was not what I expected. I have to agree with mazinger_z, in that, I was expecting a little more action, since that is what most post-apocalyptic movies tend to deal with.
Despite that though, I still thoroughly enjoyed the film. I knew nothing about it going in, other than it was a post-apocalyptic picture. I didn’t even know it was based on a novel until I came into this thread.
One question I have though: Why did Charlize Theron’s character feel the need to abandon her family? Did she feel she would become a burden on them? Or, that life was just so hopeless and she’d just rather die?
The latter. She had lost all hope for the future. Bleak, bleak, bleak.
Can you imagine if the book had ended with the kid starving to death?
My line of thinking is completely reasonable in a scenario involving a collapse of government and economy but not a collapse of the environment itself.
The Road is fairly unique in that it presents a world where nothing is left alive; no plants, no animals, no sunlight, no possibility of farming, nothing to eat but stored food stocks and other people. OK, in that situation I grant you that my reasoning would not work. Fine, I’m not arguing that it would.
Just saw this.
Michael K Williams and Garret Dillahunt were very good in their small parts, but overall I didn’t like it. In between the gory horrific parts, it was dull.
There was something very eerie in simply the looks and manner of the family who kept a basement full of people to eat though - I’ll give them that.
When he came on I wanted to yell “Omar’s starving!” but I thought that would be too much.
The ending is pretty silly. Even if they mated and had a dozen kids, the lack of genetic diversity means the end of humanity anyway. Just slower and even more depressing this way, slowing breeding inbred messes who finally will starve to death because of their inability to find food.
We don’t know that those are the only people.
It’s been almost a year since I’ve read the book, but I didn’t get the impression that the family was looking to repopulate the earth. It just seemed to me that these were a few people the boy could travel with without fear of being eaten. That they still had the humanity to care for another person outside of their group.
And as I remember it, they never trusted the man, even from a distance, and would not approach the boy until the man was dead.
So, compassion it was, I suppose, but only when it was truly safe. 