Imagine if you're the CEO of the company and you own 100000 shares of it. Then your net-worth between 100$/share and 120$/share will differ by $2 million. Quite a difference, isn't? And I think most board members hold certain amount of company's stock, and usually most people want their net-worth to grow as much as possible, so they try to do certain things to increase the stock price.
That's one of negative things about stocks in general in my opinion, because people quite often have short-term (lasting a quarter or two) outlook.