If you owned a business that had a bunch of cash sitting around with no useful growth opportunities to invest it in you wouldn't keep it in your business's bank

If you owned a business that had a bunch of cash sitting around with no useful growth opportunities to invest it in you wouldn't keep it in your business's bank account, you'd pay yourself and spend the money on a vacation or invest it elsewhere. Same with a giant corporation. Its shareholders want to be invested in a business. Owning part of a business that is 10% just a giant cash pile isn't necessarily appealing. The corporation should return the cash to its investors so they can decide what they want to do with it.