Just as there are two sides to every story, what you think they need and what they think they need are likely different stories.
And then there is a third story, the actual story, right? A needs assessment aims to find the true story by dissecting the problem from all viewpoints and uncover the need that truly fits the problem, the need that in answering will be best serving the consumer (remember that instruction and training, product industries, and service industries all have consumers).
Sometimes we think we know what is best and try to thrust it upon the world, but then it doesn’t work because it isn’t solving the right need at the right time or to the right demographic. Sometimes, the consumer demands something and then feels dissatisfied with the results because their true need wasn’t met. These are situations when a need assessment can help. If you want to start an instructional design project or new business venture, it is essential to have an in depth understanding of the real need of the consumer; get to the heart of the matter.