I think this can result from cases where paraphrase isn't useful but still culturally expected. For example, you often need to introduce the central point of another paper before you can comment on it, and the ideal way to do that would be to insert the whole abstract verbatim, but people look down on that. So, you end up writing a paraphrase as faithful to the original as possible while still being superficially different. If you're good at English, you can paraphrase in a way that flows well and displays your understanding. ESL writers might be at risk of screwing the wording up, not noticing, and getting ridiculed for poor research.