It can be very easy to get caught up in your application or website and lose some objectivity or focus.
The authors' conclusion -
"...the most important thing to gain through user research is a deep and meaningful understanding of your potential users. This can guide you through all aspects of development, including coming up with marketing and advertising strategies."
Research Guidelines You Won’t Find in a Textbook - article by Demetrius Madrigal and Bryan McClain for uxmatters.com