There are much better ways to determine the state of the economy beside just the stock market. Unemployment numbers, Gross Domestic Product, and the GINI index are all important measure of an economy's health. Of course, the stock market is one piece of a larger picture, but it is not the only one.
While it can serve as a direct indication of the state of the economy, the essential function of the stock market was not to attain this position. Fundamentally, the stock market exists for corporations and individuals to participate in professional transactions. The birth of the stock markets power can be attributed to the fact that a majority of the wealth of the American people is invested in this market.