Mainly because the supply of gold in the universe is limited and cannot expand to meet the needs of expanding economies but, in particular, the combination of a gold standard and fractional reserve banking was toxic all during the 1700s and 1800s after the initial infusion of new world gold into Europe petered out. There were cycles of expansion of fractionally gold-backed dollars and then collapse as bankers called everything back with higher rates and what came back was homes, farms, and capital assets; there wasn’t any new gold being produced to come back to pay interest on loans based on any sort of a 10% reserve.
I don't agree that the money supply needs to expand as the economy expands. With a stable money supply, prices would adjust downwards instead of upwards as they do now. In other words, the purchasing power of the currency would increase.
the combination of a gold standard and fractional reserve banking was toxic all during the 1700s and 1800s
Yes, it was. But fractional reserve banking without any semblance of a standard to fall back on is even more toxic. And, despite the bank-skullduggery, the recessions were short and, once over, prices reverted quickly to pre-boom levels.