Many board games have clear victory conditions that encourage you to play (& maximize) within the rules to achieve a specific goal. They offer an end point in what might otherwise be an endless treadmill.
Goals offer the same end point in projects. If you don’t have a goal, you won’t know when to stop. If you don’t have a well thought through goal, you might use the opportunities that occur to achieve an outcome that isn’t required.
With investments, if you don’t have a goal set, you don’t know when to stop and take the benefit (or minimize the loss) of that investment. Holding on to investments might pay off, and it might not… a goal focuses your attention on making a decision.