Of course there are several reasons to cite your sources.
All claims must be based in provable facts. If you state that children who participate in after-school activities do better in school, you must cite a research article that finds this to be true.
When you use others' words, creations, and ideas, it's important to acknowledge that their labor helped you produce your own work.
Did your professor require you to use three to five academic articles in your research project? Your citation list shows you did the work of finding, evaluating, and properly incorporating the sources, into your project
Perhaps a quote that you used from an article piqued your reader's interest. Or maybe your professor wants to double-check the publication date. Your citation provides all the information necessary for your reader to find the source on their own.
The conventions of scholarly conversation call for its participants to cite their sources. Citation shows that you know how to follow the rules.
Plagiarism is taking other people's words and ideas and trying to pass them off as your own. Failing to cite--or citing improperly--can often make it look like you're trying to take credit for something you didn't do, even when that's not what you mean to do. Proper citation shows your professor that you are using outside sources appropriately and not cheating. Plagiarism is covered in Module 7.