[roguecoder]

You can think of a share as a bet on the future potential value. So past value was previously reflected in the share price, but sometimes high profits mean that the growth is over because there's not useful R&D to be doing, whereas sometimes low profits mean that growth is ahead. Future performance is also highly uncertain and influenced by external factors: geopolitics, demand for the product, other competitors, outside innovation, taxation changes, people's relationship to the CEO, the marginal cost of that investment relative to other similar investments that serve as close substitutes, etc. All of that information is going to be part of the price of the stock, because all of that information influences the future of the company.

Plus then since the future is unknowable, it's tied up with investor's personal risk profiles, discount factors and some straight up sentimentality. If you have a crystal ball and can predict the future perfectly, stock prices would correlate with profits, but even if the market was perfect, current profits would be related to past stock prices, not current stock prices.

(Oh, and to make it more complicated and basically impossible to model with linear equations, if you own stock you can influence those future outcomes both directly via shareholder activism and indirectly via the effect you have on a company's cost of capital, so the whole system is dialectic.)