Sorry if this question is stupid, but:
Why we should use web-hooks for payments if paypal responds with correct statuses and information about payment, payer, sale etc. when we create payment via REST PaymentAPI. The same with payouts.
Probably I don't know something?
The user (purchaser) has the option of using funds from his/her PayPal wallet (PayPal funds), linked credit card(s), or linked bank account(s). Just because the payment has been executed does not mean the funds have been transferred, especially in the case of linked bank account(s). Funds from a checking account, etc. can take several days to transfer.