Here are two reasons why Indian students plagiarize, as explained by an academic Prof. Rohini Muthuswami from the School of Life Sciences, JNU: 1. Many students don't know what is so special about plagiarism when they have been conditioned to answer verbatim text from the textbooks all through their academic life, and 2. Many simply can't write properly, logically, piecing together all the points.
Read more in this post about the plagiarism by Prof. C.N.R. Rao (and his co-authors)