But you purchased a property at value X and likely have a mortgage to cover the majority of that purchase. The lender takes a risk, sure, but if you want to sel

But you purchased a property at value X and likely have a mortgage to cover the majority of that purchase. The lender takes a risk, sure, but if you want to sell the property, you still owe the lender whatever the principal balance on the mortgage happens to be, regardless of the sell price of the property. If you sell the property for 50% of what you paid, you still owe the full amount. If you default, the lender takes a loss, but you also take a loss in your credit and won't be able to get a new loan. (And they will continue to try to collect.)