Well, according to the Integrity Code at Princeton University, "there are a variety of reasons for acknowledging the sources upon which you have built your own work. [Here] are the key reasons:
To distinguish your own work from that of your sources.
To receive credit for the research you’ve done on a project.
To establish the credibility and authority of your knowledge and ideas.
To place your own ideas in context, locating your work in the larger intellectual conversation about your topic.
To permit your reader to pursue your topic further by reading more about it.
To permit your reader to check on your use of source material."
"In all of these reasons, the essential element is intellectual honesty"