Under this system, problems arise through the improbability of the wants, needs, or events that cause or motivate a transaction occurring at the same time and the same place.
Having a monetary medium can resolve this issue as it provides freedom for the former to work on or give away other items of interest, instead of being burdened to provide a particular item to the latter, impeding innovation in the long term, especially if barter was implemented on a larger scale.
Besides barter, other kinds of in-kind transactions also suffer from the coincidence of wants problem in the absence of a medium of exchange.
John Hickman argues that barter may characterize future interplanetary trade because the much lower costs of communication compared with transportation will make a shared currency between the economies of the two worlds impossible.
All of these transactions entail an improbable coincidence of wants and events which can be resolved by the existence of a monetary medium.