Most people are unaware of their true needs
The trained observer can often spot difficulties and solutions that even the person experiencing them does not consciously recognize. It is because most people are unaware of their true needs, and discovering them requires careful observations in their natural environment.
Once an issue has been pointed out, it is easy to tell when product designers have hit the target. The response of the people who actually use the product is apt to be something like, “Oh, yeah, you’re right, that’s a real pain. Can you solve that? That would be wonderful.”
If you want to learn more about how exposure to your product (or service) can affect people’s perception of it, I recommend the great book on this topic by Don Norman: Emotional Design.