A few people have brought up that dividends are not guaranteed. Which they are not. Nothing in the stock market is. But it's as close to a sure thing as you can get (when taken in aggregate).
Take a look at this chart that shows dividend growth of the S&P 500 over last 60 years.
And the S&P isn't even a Dividend weighted average.
AT&T doesn't raise their dividend much these days, but they pay 5%. If you hold it 10 years, you've already gotten 1/2 your money back.