Also I'm pretty sure they are making enough money as they are. And don't need to chase that ever increasing stock valuation. Which might not even mean increased profits.
Apple going from 1 trillion to 2 trillion valuation is much more valuable to shareholders than Apple paying out 100 billion in profits. But if the stocks aren't publicly traded then the main pay-out are the profits, so they try to maximize profit over growth, which is probably much healthier for the economy overall.
The two are intricately related.