Research papers are written to show that the student can do extensive research on a topic and gather their thoughts into a paper. Usually the research paper provides proof to the teacher that you know the topic inside and out. Due to the extensive research at the library and online, there should be plenty of facts and evidence to support your claim or topic. In this manner, the student would appear as an expert.
Sometimes, research papers are written and published so that others can use the information that you gathered and wrote to be used for other writings. Experts on the topics are usually consulted when writing a research paper so that the student has plenty of facts to use.