Why would someone want my product. Why am I creating my product. The designer should be able to truthfully answer these questions. The problem is that in design, whether for products or engineering aspects of our own lives, people are prone to fantasy. They assign motives to users that do not exist. They assume their interests will persists into the future. They are unrealistic about both themselves and others. Consequently, the Internet is littered with websites, Facebook pages, YouTube videos, etc. that are ignored and largely forgotten.
In design, we must strive for clarity in answering the question of "Why"? Clarity can be difficult to achieve, but allows the designer to operate with a realistic understanding of "Why." This applies to the intended user or customer, and their needs and abilities. But, it also applies to ourselves and understanding the real reason for why we are inspired to create something new or do something different.
There is a simple rule of thumb worth remembering. At its' essence, the human brain has been engineered to maximize the occurrence of pleasant experiences, while minimizing unpleasant experiences. This rule of thumb offers a good place to start when answering the "Why" questions for ourselves and others.