The investing world is extremely set in its ways.
Since the advent of enterprise, people have invested time, labor, intellectual property, and money (when it came into existence) in business. At first, this took the form of throwing in your lot with a friend or neighbor. The two of you would shoe horses, or bake bread, or plow fields in exchange for some other service. In time, some metals began to act as a medium of exchange and a storehouse of value. We think of gold and silver today, but tin, cattle, rocks, diamonds, and other portable elements acted as a clearinghouse for services in different regions and at different times.
Eventually, some people accumulated enough wealth as measured in the local community to invest in other businesses. Initially, this was done directly, person to person; since exchanges developed it has been possible to invest in equities nearby or far away, either to benefit from their success or lose your shirt along with the owner when the bubble bursts or the market turns. Over time, investing in stock markets has provided investors the world over with what are considered superior returns on the capital invested.
On the borrowing side, first monarchies and then companies obtained funding from the community in the form of loans. As more money was needed from a wider audience, these became subdivided like stock into shares called bonds. Bondholders own the opportunity for full loss of principal like ...