Apple has $150 Billion in cash, yet it has decided to issue $17 Billion in new debt to fund its stock repurchases. Why not just use cash on hand? One reason is that almost 90% of the cash is held outside the US, and repatriating the cash would trigger significant tax liabilities. Another reason is that interest rates are so low, and if Apple can earn a higher return than the cost, the added financial leverage will be a benefit to shareholders. (See article here, CNBC.)
Dolvin, Steven D., "Apple Issues Debt to Buyback Stock" (2014). All Chapters. 100.