Because the stock is now the core product for many businesses and they basically all come just short of conspiring when it comes to what rules indicate healthy or weak businesses. The value is not as attached to how these businesses actually operate or how their alleged core products are doing anymore. The stock is the product, and everyone involved has incentive to see it grow grow grow no matter what.

The big dogs like M$ burn tons of money on acquisitions and mergers, which makes them look healthy and growing. Then they layoff thousands of people at a time, because that means they’re ruthless and efficient and have a great balance sheet going into their quarterlies. Both of these decisions make the stock grow almost every time.