In case something random happens like they get fired or have a child they'll be forced to start selling things they own.
One problem of our age is also that everyone want to live in a big city, since they think they will earn so much more money if they go there. The problem is that they only see how much more money they would make, but not how much more the average cost of living also will be. So many people actually change their live to the worse by moving somewhere, wehre they don't own anything and have to start from new.