Why were joint stock companies necessary for overseas trading voyages?

In the 17th Century, English merchants used Joint-Stock companies to pull capital, and, share the risks associated with voyages to Africa and Asia. They were similar to modern corporations that sell stock to investors to pool resources like money or capital together for research, new product development with a goal, to make profits and reward investors with an increased share of their stocks. The risk was small but the returns were fairly quick.