Just observing what people do and how they interact with the environment gives us clues as to what they think, feel or need; have they frowned?, Are they worried?
We are not aware of all these things because our brain filters all this redundant information (for us) and we do not get to the problem: but if we empathize and put ourselves in their shoes, things change.
But it doesn’t end here, because the user may not even be aware of the problem he has, and that’s the magic of design and human behavior. We do not do what we think, nor we do think what we say, nor we do what we say.
It is very important to discover these needs (previously discovered or to be discovered), guide the research efforts, identify the most representative users and finally, and most importantly, discover the emotions that guide these behaviors.