Two main reasons:
Scholarly Tradition (as in, centuries of tradition)
&
Copyright Law and the Fair Use doctrine exception
Scholars like you (Whaddaya mean you don't 'feel' like a scholar - you're a scholar!) learn from others. They always have. They always will. And one of the main academic traditions is that you give credit to the people you've learned from. As for Copyright law and the Fair Use doctrine - I see your eyes glazing over; stop that! - copyrights are author's (creators') rights. This bundle of rights gives the creator exclusive rights (for a while; not forever) to do stuff like make copies and sell them, in other words...to make $ off their intellectual property! Creators also always keep the right to be known as the person who made that creation - it's considered such an important right that it's what is known as an author's 'moral right'.
Fair Use is an exception built-in to Copyright law that lets the Public use a little bit of creators' works to do things like...write papers in the university course they're taking. (See; that explanation wasn't so bad, was it?) But you have to give credit to the creator/author. (See how this is all coming together?)
Quote and paraphrase stuff from other peoples' works to make your points in your papers, but cite those sources correctly. If you use other peoples' work and don't cite it (including stuff like pictures, photos, music, video)....that is plagiarism. Doesn't matter if you plagiarize by mistake (you're not sure how to cite correctly, you forgot to include a citation for something you put in your paper, etc.) or on purpose - it's a major breach of academic ethics. Won't get you arrested, but might lead to you getting an F on an assignment, flunking a whole course...or if it was bad enough...getting kicked out of school.
So don't plagiarize.
Some professors get really strict about you doing citations correctly, and may even take points off for mistakes, so always double-check that your citations are done correctly according to which citation style you're using. (Just compare how they look against the examples from any decent style guide.) Check even if you use citations that our databases offer you, or if you used a citation management app like Zotero.
By the way - we Research & Learning folks don't mind helping you check your citations, if you're not sure you did something correctly, or answering questions about how to cite some less common source (such as stuff from the internet).
You know where we - and our walk-up Help Desk - are. (You do, don't you?) Upper Mezzanine, up the stairs from the main floor, on the parking lot side of the building.
- Research & Learning