Giving Credit Where Credit is Due
Acknowledging sources is an ironclad rule in the world of academic research. Not only are intellectual property rights at stake, but the simple notion of doing the right thing, as well.
Individuals who have pursued a specific line of inquiry and have made a significant contribution to their field of study deserve recognition; it's their due. More importantly, giving credit eliminates suspicion of having taken credit where credit isn't due.
Keeping "who said what" organized allows for an orderly presentation of ideas. Accurate documentation ensures a tangible background of verifiable sources against which the trustworthiness of someone's findings or conclusions can be measured. It also creates the foundation upon which future inquiry and research can be built.