Man's and most other animal's nature is to stockpile resources as much as possible for times when they're not available. Because in the wild, this is the best survival strategy as it is very rare to be in a situation of guaranteed long-term abundance of food. That's why, as the above picture illustrates, we get fat in a setting of industrial civilization with cheap and abundant food - because our physiology is such that we are very good at storing excess calories in the form of fat for lean times and it is very difficult to overcome the desire to continue stockpiling it even though realistically lean times will never come. Also, because situations of such long-term abundance are extremely rare in nature, where intense intra- and interspecies competition for resources is the norm, our physiology is also very bad at dealing with the negative consequences of the kind of extreme obesity we see these days. It was impossible for people to get that fat so there was no selection against developing diabetes, heart disease, etc. as a result of being fat, and people died too young for this to really matter anyway.
Exactly the same effect applies to everything else we do - we desire more and more because our brain is wired towards stockpiling physical resources when they are available for the purpose of using them in times when they're not readily available and for the purpose of impressing potential mating partners. We live in a very different situation now when not only is there no need for that behavior, it is in fact self-destructive (just as overeating leading to obesity and poor health is), however our brains, hormonal control of emotion and physiology are still those of wild animals living in environments in which that kind of behavior was good for us and we can easily overcome our primal urges. and with