The effect you're referring to is caused by speculators who predict that growth will continue and bid up the stock price, which then falls back to the baseline when the prediction is shown false. Companies should stop eating their seed corn just to keep quarterly profits above the level dumb speculators predicted it would be, at the expense of the long-term health of the company. But most of them probably won't as long as executive compensation is tied to short-term numbers rather than long-term numbers.