Why does the equity method record dividends received from an investee as a reduction in the investment

Question:

Why does the equity method record dividends received from an investee as a reduction in the investment account, not as income?

Dividend
A dividend is a distribution of a portion of company’s earnings, decided and managed by the company’s board of directors, and paid to the shareholders. Dividends are given on the shares. It is a token reward paid to the shareholders for their...