This seems kind of obvious, but OK. How do you know what a customer needs? How do you know whether your idea meets that need? You have to look at the world from their perspective begin to answer those questions.
Follow-up question here, as I have just come from attending a focus group this evening. Is what you describe a typical part of the job description of a Web designer (what prompted my question above) or is it really the job of, say, a focus group facilitator?
A focus group facilitator doesn't try to influence the audience. And focus groups usually don't even empathize with the customer, they simply write down what the customer wants, if they prefer blue or red, not why they prefer it and what that says about their overall goals.
How do business results show the benefits of empathy?