What is the most important reason to cite evidence in an argumentative essay?

To show your reader that you've done proper research by listing sources you used to get your information

Arguments are claims which are supported by reasons that are given by evidence. They are important because they show the reader that proper research has been done while collecting the information and to be a responsible scholar by giving credit to other researchers and accepting their ideas in your research. Evidence is not accepted until it is proved by providing correct information and sources.

a pirate walks into a bar with a steering wheel sticking out of his pants.

bartender: isn't that uncomfortable?

pirate: arrgh! it's drivin' me nuts!

pretty sure 1.someone's coat was found in the lobby.