Indeed - 'capitalism' is about the allocation of saved capital to investment in a largely unregulated marketplace of goods and services. The rise of capitalism and free markets spawned shared capital markets as investments got too large for even the wealthiest invididuals to solely fund.

The instant-casino-trading side of things came much later along the road. It's not crucial to capitalism to the level people might think it is.

The arch-capitalist Warren Buffet regularly says he'd be happy for markets to close for a year. Though that refers to equities and not forex, which obviously does need to stay open to allow trade to happen.