Why do they keep the car if not being used?
Good question. They didn't want to sell it because they said the car wasn't used much and the large depreciation. They might not understood that the car if unused is not good for it. They might had thought a car stored away is like buying an extra microwave for contingency. In the past I also had to tell them to don't buy an extra smartphone or cellphone (prior to smartphones) because the battery can go bad, phones go out of date and telco's can discontinue the support of 2G etc ..
Edit. They also didn't want to sell the car saying it wasn't used much hence thinking that car is in tip top condition.