In fairness what reason would they have not to? If more people buy it pushes up the value of their stock.
For the reason of buying as much of undervalued stocks as possible before stock's price finally catches up.
...From my limited knowledge of stocks, dividends depend on the success of the company and so it's not really possible to know exactly what a dividend will be until you're due to receive it and you need to own the stock in advance of that.
That depends on the entity's dividend policy, size of its distributable reserve and nature of industry. It's not like it's a total surprise until the dividends are declared. Large companies are pretty good in forecasting performance, therefore you can know well in advance what kind of dividends you can expect in 1-2 years.
Plus, if you hold shares with voting rights, you could co-decide on dividend payment.