Your historical explanation is reasonable and rational. The problem is that compulsive hoarders and eaters aren't. I mean there are persons that like to hoard, persons that like to eat much, but the extreme cases involve a personality disorder.
"Eat as much food as possible" and "hoard useful resources" have been successful evolutionary strategies for pretty much the entire history of life on earth. Abundance is very, very new. No species can fully adapt to a completely different ecosystem in a few generations. Most of us have at least some maladaptive responses to abundance. Some people eat too much, some people own too much stuff, some people drink too much alcohol, some people are scared or sad all the time for no obvious reason, some people lose their life savings to imaginary internet money, some people spend an unreasonable amount of time playing Candy Crush or reading Hacker News. We're just not built for the modern world.
I'm not endorsing hoarding as a lifestyle. I'm not saying that it's healthy or rational. I'm not saying that we should leave hoarders to their own devices. I'm saying that it's not crazy, just an obsolete strategy. Looking through that lens gives hoarders a means of understanding their behaviour and gives us a means of helping them.
I think that's a perfectly reasonable definition.
One anecdote was a woman I know who (when someone cleaned out her nearly condemned) house became enraged that he was "getting rid of all her memories." The thing has supplanted the good feeling of having the thing.
"Nostalgia marketing" does this. How many versions of Monopoly do you need?? Well, here's one with the ORIGINAL TOKENS and WOODEN HOUSES!! And here's one with SPONGEBOB SQUAREPANTS!! and OHIO STATE FOOTBALL!!!! You need them ALL or your life is incomplete.
At least for eating, most people don't operate rationally; can you tell me how many calories you ate and burned today? yesterday? I can, but I have been putting a lot of effort into this for some time now. most people don't know what they ate yesterday, unless they eat the same thing every day. Most people operate on instinct. I've operated on instinct for most of my life, too; I was super skinny as a teenager, healthy in my early 20s, then growing into overweight but not obese in my late 20s and early 30s... then obesity set in during the mid to late '30s
This really was pretty steady; my strength changed a lot; during that period my bench press would go from 50kg to 100Kg and back again multiple times, but my weight just continued to very slowly increase.
Clearly, whatever subsystem decides "I'm hungry" or "I'm full" is tuned to get me to eat just a little bit more than I need to maintain my body. And it's pretty good at it. If I work out? the more I work out, the more I want to eat. working out without caloric control simply doesn't work to lose weight for me.
I've been counting calories in and out (and trying to run a small long term deficit without otherwise spending a lot of effort on what I eat) for some time now. I have gone from a BMI of 31 to a BMI of 26 in the last year or so. This after trying a bunch of "eat this not that" diets, which have never worked for me. But I have been... slightly hungry for the last year or so, and thus I think about food and my relationship to food a lot.
My theory? My theory is that my farming ancestors found it advantageous to eat a little more than they needed when food was around; that it was better to carry that bit of a belly around all the time if it meant that you wouldn't die if you didn't stash away quite enough grain for the winter.
(As an aside "just eat less" "stop when you are only slightly hungry" also doesn't work for me; that ends up with me eating way less than I need to for some reason (I need to come within 20 or 30% of my maintenance caloric intake, from experience, or after a few days I enter a semi-fasting state where I'm tired and can't focus - I'm guessing this is also the farming ancestors. "Oh, there isn't enough food stored? Maybe you should take a lot of naps until this year's crop is ready to bring in")
If I can find the source I'll add it later, but I've also read research that suggests that even the most active hunter-gatherer tribes in Africa, who might walk 15-20km per day, still burn about the same amount of calories as the average American. Yes, they are certainly more fit, but it might just be that the stronger you get from working out, the less calories you burn anyway.
And quite a story. ConceptJunkie explained elsewhere in the thread what I consider to be a disorder: a behaviour that harms yourself and, even knowing it's wrong, you are unable to stop.
Most people has mild variants of self-defeating behaviour in some areas. The problem is when they mess severely with our well being.
You know you can't really blame your farming ancestors, they adapted to whatever changing conditions they found. You are expected to do the same. FYI limiting carbs is more convenient than counting calories and much more effective.