Why do we need an Engineering Notebook?

I have seen a few questions regarding the definition of a bound notebook. I was wondering what this notebook is needed for and if it is necessary.

The Robotics Education & Competition (REC) Foundation seeks to increase student interest and involvement in science, technology, engineering, and mathematics by engaging students in hands-on sustainable and affordable curriculum-based robotics engineering programs. The REC Foundation develops partnerships with K-12 education, higher education, government, industry, and the non-profit community to achieve this goal.
The REC Foundation’s vision is to change the world by inspiring young people in all communities to pursue degrees and careers in STEM fields by providing access to high-quality programs and by helping students acquire real world life skills that will benefit them in their academic and professional future.
Learning to thoroughly document their team’s work in an Engineering Notebook is one of those skills. The Engineering Notebook is a way for teams to document how the VEX Robotics Competition experience has helped them to better understand the engineering design process while also practicing a variety of critical life skills including project management, time management, brainstorming, and teamwork.
The engineering notebook is required for teams wishing to be considered for the Excellence and Design awards. The engineering is not required for other judged awards, however team mentors should always keep in mind that the goal of the VEX and VEX IQ programs is student growth and that learning to keep an engineering Notebook is an important factor in that growth.