for a multitude of reasons, generally to fund a merger or just to offer more of the company to the public. Companies can split shares thus increasing the float, or shares available, but when that occurs no money is taken by the company. If a stock is 100 and splits 4-1 the stock is worth 25 the date of the split, but the numbers of shares outstanding increase by 4x. The only time they receive direct investment from the "public", investors is by IPO or secondaries in the stock market. They can issue bonds to get investment but that's a different animal.