The provenance problem
Quizlet's library is its greatest asset and its sharpest edge. A set that matches your course is a gift; a set that nearly matches it is a liability, because you cannot tell which cards are wrong until the exam tells you. Definitions drift between textbook editions, professors emphasise different distinctions, and a set built for a different syllabus will be right often enough to feel trustworthy and wrong exactly where the marks are. Cards generated from your own lectures do not have that failure mode — the source is the course you are actually taking.