the primary reason for the stock market is to raise funds to start or expand a business venture, later the people who participated in the IPO want to sell, someone has to buy it and the only reason to buy it is for future capital growth, dividend payments or to participate in further capital raisings to expand(or unfortunately to stop going bankrupt) the business. everyone who participates in the buying and selling of shares supports this process and hence support employment
Liquidity is paramount to any share and the market as a whole