Why do people let their planes rot?

More of a rant than a question, but I wanted to see people's opinions. Almost every small airport has a plane or a few that are seemingly abandoned. Meanwhile the GA fleet is slowing dying off. It's sad to see. I tried to buy a plane that had been sitting for 2 years, the owner had lost his medical and had no chance / intention of getting it back. I made a fair offer for a plane in the condition it was in. The owner responded that he would rather keep it if it is only worth that much. Why? Just to spend $100 a month to tie it down? Why do you all think there are so many abandoned airplanes sitting around?