In a capitalistic system the flow of money can be unsymmetric, with a certain amount of people accruing more and more, at the expense of others. In such a system there has to be growth in the total amount of money for the economy to survive. In a timebank, the flow of money is symmetric, people oscillate around the zero point of credits, but are never continually increase or decrease.
One can make the argument that a symmetric flow of money in an economic system is usually healthier, that it creates balance. When symmetric breaks a phase transition to a higher level in a social system happens.