By delaying payments Apple can use the cash for other short-term investment opportunities. In Apple's case, their accounts payable is probably in the billions. As an example: If Apple has a $10 billion accounts payable and instead of paying it right away they waited for 3 months and invested that $10 billion on short-term securities with a 10% return, Apple would earn $1 billion in that 3-month period vs. ZERO if they paid their liabilities right away.