MA students pay, and overseas students pay around three times what home students pay, in the UK at least. The universities need the money - they get very little money from government or undergraduates, certainly less than before. It's bad business to fail a paying customer, and if everybody's being lenient there's less risk to your institution's reputation, I suppose. It's also true that in order to attract more students, many universities have lowered their requirements for English proficiency too far - some MA courses only need IELTS 5.0 score, and that's too low in my opinion. Of course these students struggle to complete courses that are supposed to be testing even for native speakers of the language. There's also the cultural issue that many overseas students are coming from education system that not only tolerate plagiarism, they encourage and require it. It's part of our Western culture to value the students' own words, but many non-Western teachers would say it's better if students can simply repeat the words of the 'expert' verbatim.