Options are one of the best tools we have to price uncertainty in the value of publicly traded companies. The option prices allow you, using Black Scholes, to c

Options are one of the best tools we have to price uncertainty in the value of publicly traded companies. The option prices allow you, using Black Scholes, to calculate an implied volatility that can be used quite similarly to the error bars on a measurement. The EMH would say that a company's stock price accurately reflects all current knowledge about a stock's underlying value. So from the point of view of an investor in publicly traded companies, a stock's price and its underlying value are the same thing. Options have an expiration date because as the further you go out the more uncertain things are, and the harder it becomes to make a market in options in a way that (a) won't result in a high chance of losses and (b) will have someone actually willing to buy them. That's why you don't see 10, 20 or 50 year options. That doesn't hurt their value for pricing uncertainty because as options expire, new ones are minted. Therefore, you can always use them to price the uncertainty of the price to the next quarter, the next 6 months or the next year.