Final answer:
A valid contract may be unenforceable due to issues like lack of capacity, expiration under the Statute of Limitations, lack of consideration, or illegal purpose, all of which can undermine the necessary elements of enforceable agreements.
Step-by-step explanation:
A valid contract could become unenforceable due to several reasons such as lack of contractual capacity, application of the Statute of Limitations, absence of consideration, or if the contract has an illegal purpose. For instance, in the context of property and contractual rights, when a skilled surgeon performs a surgery on a patient, there is an expectation of payment.
If payment is not made, this equates to the theft of the services provided by the surgeon. In a robust legal system that upholds contractual and property rights, the surgeon would be able to enforce the contract and seek payment through the legal system. However, without such enforcement mechanisms, contracts for future services would become riskier as parties may fear non-compliance and thus potentially slow economic growth.