Black Scholes applies to European options that have a fixed exercise date. Black Scholes cannot reliably be used for American options that can be exercised at any time. American option prices are estimated using lattice pricing models.

There is also the issue that the market price of an option often differs (sometimes substantially) from the modeled price. Options are priced in the market. In theory market prices will move toward modeled prices. Unless market actors believe something about the future that is not reflected in the options model.