They are "lucky" that they can walk off after handing over the keys to the house even when the house value has depreciated to far below the sale price. Places like Australia, the bank has the right to chase you up for the debt AFTER foreclosure if the house value has decreased.

This is a bit like maxing out the credit card. It's tough for the children and unfortunately a lesson has to be learnt by the parents not to live like the "moviepass economy"