A collective obligation

By injecting shemittat kesafim into the core body of covenantal law the Biblical author is guaranteeing a basic level of security in the society. 

Unlike corporate debt, personal debt is always an indicator of insecurity. The Biblical admonition every seven years to release personal debt without loss of dignity, coupled with the requirement to help kinsmen to meet their mortgage payments and to redeem foreclosures on real estate combines to define the maintenance of a certain basic level of security as a collective obligation. 

The incentive system of the individual choosing decisions in a free market environment works well so long as the circumstances of the decision-makers are discretionary. Once the decisions pertain to the mandatory, to the inalienable aspects of existence – basic food, shelter, health care – the apparatus of the collective must kick in. 

As expected, the matter of shemittat kesafim is a matter of what is alienable vs what is inalienable, and upon whom falls the responsibility to secure what is inalienable.