Joannie - The share market does "benefit others" in three important ways. As a primary market, it enables capital to be raised (through IPOs, placements and rights issues) for enterprises to conduct their business; and as a secondary market for the original providers of equity and all subsequent purchasers of said equity, to transfer their ownership interests.
The third benefit is that the deeper and broader a market, the more liquidity (thus ease of buying and selling) and the more likelihood that a portion of a business is fairly priced i.e. closer to its inherent value that would be received in a privately negotiated transaction.
