1. It is costly and the cost is unnecessary (maintaining, transportation, environment cost of digging for gold).
2. Under the gold standard currency can not be expanded in response to increase in trade.
3. The supply of currency depends on the supply of gold but the supply of gold depends on the success of the mining which may have nothing to do with factors affecting the growth of trade and industry.
4. Gold movement leads to changes in interest rate which affects investments and thus affecting the money income.
5. A country on gold standards can not follow an independent policy. In order to maintain the gold standards or restore, it may have to deflate its currency against its will.
Wilfykil answered the question on March 8, 2019 at 10:11