What prevents investors from buying high yield stocks and selling them as soon as their dividend is paid out?
This investment strategy may have tax advantages. In some countries, income received from dividends is taxed as income, whereas profits on share trades are capital gains. If you have already exceeded your tax-free income limit for the year, but not your capital gains tax allowance, it may be preferable to make a dealing profit rather than an investment income. These arrangements are called a bed-and-breakfast.