A reason that owners let their cars sit and rot

People now a day think everyone is broke and need to give their car away. I have a nice survivor 86 Mustang GT convertible. I think its worth 4 grand. The guys that want to buy it offer me 2 grand. I will keep it. I don't drive it much, but I wont give it away either.
Oh and another thing, there is no "For sale" sign on it. It is annoying when people waste my time with their crappy low ball offers. It is funny that people will always want what you have. It doesn't matter what it is if you know what I mean. If I was a younger angry man, it just may piss me off, but I am to the age where I can pick and choose what to get pissed off about. As for my 340 Dart, I have paid for a rented storage unit to store that car for 20+ years. I have since built a garage at my home and life is good. I can work on it whenever I get the urge. I have saved that car from going to the scrap pile in the early 90's. It is still in body and paint phase, but I have all the parts to complete it. If I were to sell it, the price would reflect my investment in the preservation of this fine rust free specimen of an H code car. I know I will not get all of my investment back, because some expense is considered loss, but the hard body work is done it is prep and paint / assembly time. The buyer would not understand that and lowball me. People want but they don't want to Pay.