This is a phenomenon we call hoarding. Arguably, hoarding is one of the most important instincts that led to the divergence of man from other primates. In essence, hoarding should be perceived as the instinct of recognizing utility and anticipating the future use of material objects. When our cave-dwelling ancestors randomly picked a chipped stone that could cut meat particularly well, they had the instinct to preserve that particular stone for future use rather than hope to chance upon a similar implement the next time the need arises. This act would save much time in the future, making man more efficient in exploiting meat as a source of food. With tools on the ready, man could swiftly cut up captured animals for consumption, as opposed to having to scavenge for tools once the hunt has been secured. In the entire animal kingdom, man is probably the only animal with the ability to anticipate the future use of objects. When a chimpanzee uses a stone to crush some nuts, he will soon forget about the stone that helped him crack the nut open. The next time he comes across nuts, he has to search around for another stone to do the cracking job, wasting many calories in the process. And should the area have no available stones, he may have to give up on the nuts. This scenario would not have happened to the early man precisely because he was a hoarder.
In present times, hoarders are not sick individuals but people with accentuated instincts. Such individuals can decipher possible future use for virtually every object they come across. In an environment with few material objects, such a tendency would not present a problem because hoarded objects would find some use sooner rather than later. However, in an environment marked with excessive material possessions, hoarded objects are likely to remain unused for a considerably longer time, often presenting storage problems to the hoarder.