Marx explains that the primary use of capital is to accumulate more capital. No one who invests money is satisfied with an equal or lesser value in return. Note that this is disanalogous to a direct exchange of goods. If I give you a coat and you give me a chair, we are satisfied with the trade because the use-values are heterogenous even though the exchange-value is homogenous and [if the trade is fair] equivalent. But there is no reason to exchange $100 for $100 because the two are the same. (This is not to say we should go back to the barter system: the point is that capitalist commodity production leads to capital, which leads to an expectation of infinite profits.) Once you have a pile of money, you can either sit on it or you can throw it back into the market in an effort to get more money.

Marx argues that, under capitalism, money itself becomes fetishized, since the owners of private commodity production pursue ever greater profit. More precisely, they pursue more surplus-value to appropriate from the value created by the labor-power they purchase from workers.

Name a time in history private ownership hasn’t metastasized into monopolies and imperialism. Wall Street as a financial hub didn’t even exist till 1817 and didn’t gain much hold on the world till far later. The first stock market was in 1611 in Amsterdam. British capitalism fueled British imperial rise before America even existed. Capitalism is just smaller fiefdoms under owner monarchs. It always exploits labor and slowly takes more and more power to oppress for its own gains. People are real quick to forget how awful businesses were to labor in the past. Union members died to get us the little we have they are again stripping away. Systems that centralize power with an unaccountable minority always do the same thing.