We have today a hybrid of two forms of banking — loan banking (non-inflationary) and deposit banking (inflationary if not 100% reserve holdings).  The cause of booms is the credit expansion by central banks that is not backed by pools of private savings.

In the history of money, bartering was awkward because wants were not divisible. Direct exchange depended upon a double coincidence of wants. Demand for a medium of exchange grew until a general medium of exchange emerged, like gold and silver.