Why is continual user involvement a useful way to discover system requirements? under what conditions might it be used? under what conditions might it not be used?

continual user involvement gives the flexibility to analyze the requirements in right direction. because there is continuous meetings with the end user and he can provide right direction or avoids wrong interpretation of the requirement

Explanation:

continual user involvement is useful when we are following agile methodology where we are building complex systems. it is not useful for simple sytems and following waterfall methodology