With joint-stock corporations, investors can place bets on the success of many different companies, without having to play a central management role in any one of them. This allows investors to diversify their financial holdings. It also allows them to capture profits on their investments, without having to get involved in the dirty, troublesome business of actually running a company.
Jim Stanford (2008) Economics For Everyone Part 2, Chapter 7, Companies, Owners, and Profit, p. 91.