From the company POV the capital investment is the outstanding shares. The shares need to be kept happy with some combination of immediate profit and continuosly growing projection of future profit (i.e. investing into growth), or they start to lose value in the market and become even more unhappy. Eventually investing into growth runs into diminishing returns and immediate profit becomes the dominant component.

The profit you get from buying and selling on the market is either a result of the shares being kept happy, or taking advantage of market mechanics. The latter is mostly a form of gambling that doesn't produce value.