If you have poor relationships, the quality of your code will suffer.
How you deal with people outside of your team will affect the code that you write.
Better relationships and understanding lead to better requirements and more clarity. If you don’t have a strong understanding of the requirements, there is no way your code will properly deliver the desired results.
Our goal as software engineers is to deliver business value by write code. This is measured by people outside of the technology organization. Never forget this.