Few things have as much of a global impact as the stock market. From Wall Street to Hong Kong, the market holds sway over trade agreements, building projects, the development of medicines, and the job market. Experienced investors are aware of all of this, but the average person may not put too much thought into it. The stock markets influence the way that things happen on a global scale.
For example, when China goes into a recession they produce fewer commodities which results in less jobs for people over there and fewer products being sent overseas. Don’t see how that affects people here in the United States? The decrease in supply creates an increase in demand as limited availability can force sales based businesses to increase their prices. With an increase in prices there is usually a decrease in sales numbers which can cause an increase in unemployment levels as companies struggle to maintain their overhead costs. In short, when one market suffers those closest to it also tend to suffer.
It usually is not as simple as that, but for the purpose of understanding the global stock markets the above example serves to show how investors interpret cause and effect. Stocks are constantly moving. That is the nature of the free market. Every purchase or sale of a stock in a publicly traded company has at least some very small impact on the value of that stock. Without the free market, the value of companies would be much more rigid and based on the contributions of private investors. The benefit that many investors see in the free market is that they are able to grab a share in virtually any industry that they desire.
Access to an open market is beneficial in many ways, and it can be helpful for distributing wealth to a wide number of people. Inexperienced investors can work their way in on the ground floor and build up a portfolio full of assets over time. Without a free trade market, the private investors would have the only say in how the company was moving. Free trade enables small investors to in a sense vote with their investment on whether or not they support the direction the company is taking. On a global level there is little way to have as much influence as choosing when and where to invest.