Most beginner level economics books include explanations why it is most effecient most of the time to allow free trade in the market of goods and services. (e.g. the theory of comparative advantage) However, few of them talks about similar things for financial markets (e.g. stock exchange, forex). The books will tell you how those financial instruments work, but they do not discuss whether it is the most efficient to allow free transactions in financial markets (just like the free trade in goods/services markets). Could anyone tell me if there are any theories on the topic?
What makes me curious is that, despite their huge role in our life, financial instruments are not classed as any factors of production, and seems to create no value economically. For example, fund managers are NOT enterpreneurs.
So should the government intervene to prevent speculation, or should they not intervene? Is there any theory on this?