As a university student you are trained in carrying out work at a scientific level. Some of the important aspects of scientific work are transparency, validity, and independence.
Documenting your sources and making citations to other’s work is a way to make your work verifiable and transparent.
When you cite other people in your work, you make it possible for the reader to follow your argumentation and the rationale behind your work – you allow the reader to understand how you got from A to B and which sources you have used to produce your argumentation.