Generally speaking, a dividend is a distribution of a portion of a company's earnings paid to the shareholders.
The simple answer is to attract more investors. Many companies that payout dividends are well-established and stable companies.
When it comes to dividend investing, find companies with solid track records, meaning they are well established and have high market values.
Make sure you find a company that has a payout ratio in the 30% – 50% range as anything higher could be unsustainable.
So, yes, you might find stocks with higher yields, but that doesn't mean anything if that company can't sustain those yields or raise its dividends year over year.
Speaking of long-term investing, the best way to gain the most growth from your dividend investing over the long term is to participate in the DRIP consistently.