That money belongs to the shareholders. You can invest it in the company to attempt to earn more money in the future (capital improvements, research and develop

That money belongs to the shareholders. You can invest it in the company to attempt to earn more money in the future (capital improvements, research and development). You can pay it to the shareholders in dividends. You can acquire other companies to diversify or to enter new markets. If you buy back existing shares of stock, you increase the value of each share of stock by improving the earnings and free cash flow per share. (Think of it as paying down long term debt.) Stockpiling the money--especially that much money--doesn't generate much return for shareholders. Sure, it earns a little bit of interest, but Buffett's reasoning is probably that there are better places for that money. Use it to make the company worth more.