As noted in Section 3.8, the FASB states in SFAC 1:

Information about enterprise earnings based on accrual accounting generally provides a better indicator of an enterprise's present and continuing ability to generate favorable cash flows than information limited to the financial effects of cash receipts and payments. In other words, the FASB is arguing that net income is a better predictor of future cash flows than current cash flows themselves. This may seem surprising Why do you think the FASB makes this argument?