As scientists, we must place very high value on scholastic honesty, for it is only by absolute trustworthiness that we, and science, can succeed. One important characteristic of trustworthiness in scholars at every level, including as students, is proper attribution. By that I mean giving credit for ideas and writings to the person or persons deserving it.
Plagiarism is easy to commit.
It takes neither talent nor ingenuity to copy another person's work and try to take credit for it. This is because people who are likely to read your work are also very likely to have read what was plagiarized. When that happens, the best you can hope for is that your integrity will be diminished in the view of your reader. And the worst that can happen may be very bad indeed. For example, academic dishonesty can lead to expulsion from the GSBS, or after graduation, being fired from an academic or industrial position.