Citing helps you avoid plagiarism, but it's actually important for other reasons as well.
If I say that video games are an important piece of media that contributes to the global cultural conversation, you should be doubtful of that statement. I have no particular expertise in video games as they relate to culture and how they affect the people that play them. However, if I say that noted sociologist and expert in cultural studies Joanna Smith says so and I cite a study that she published in an academic journal that supports my assertion, you should take my statement a lot more seriously. Now, as a reader, you can read Joanna's study and evaluate it to see if you agree with my conclusion. This is what your professors are looking for when they ask you to do research. The quality of the sources that you cite will make a difference in how your arguments or theses will be perceived by your reader.
Image Source: Avoiding plagiarism.
University of California San Diego.
[Accessed March 9, 2020]
In academia, getting credit for their work is extremely important for professors and researchers. Often, their employment depends on being published in a reputable journal. While all people deserve credit for their work, for academics, it's essential to their livelihood. Claiming someone else's work as your own, even inadvertently, is very offensive and upsetting. This is also true of other people whose ability to make a living depends on getting credit for their work, such as artists and musicians. Citation is a way to acknowledge that you are not the creator of that particular work and that the original creator gets the acknowledgement that they need to succeed.
In academia and scientific research, professors and researchers build off of one another's work. When a researcher starts a project or experiment, they don't create their hypothesis from nothing, but do so based on things that others have studied. Because the goal of research studies is to advance human knowledge, it makes sense to see what others have done before you, so that you can learn from others' mistakes and look at new areas of study. There's a famous phrase that describes this idea: standing on the shoulders of giants. This phrase expresses that truth is found by building off of the previous discoveries of the people who came before you. Scientists continually check themselves and their peers to test and re-test hypotheses before they conclude that they are valid or not. It is through this re-testing that theories accepted as truth in the popular press are later disproved. This process takes time and involves human error, and unfortunately, can lead some to distrust science in general. The citation list helps gives transparency to this process and is essential for it to function smoothly.