While both have multiple choice, select all that apply, and fill in the blank question types, the reasons to each are different.
Knowledge check elements in a sequence are used as formative assessments; they're checking the learner's knowledge. You can provide immediate feedback in a knowledge check based on the learner's response. Feedback for correct answers can be "Great job!"; feedback for incorrect answers can outline why it is incorrect, what the correct answer is, and why there might be some confusion between the two, creating a teachable moment.
Since a knowledge check isn't used to capture the learner's final understanding, knowledge checks are not scored. This gives the learners the freedom to be intellectually honest without feeling like they're being judged. This also means learners are not able to retake a knowledge check as the answers are a reflection of their understanding in that moment, not their final understanding.
Quizzes are used as summative assessments; they're measuring the learner's understanding after engaging with the learning material. Since they come at the end of the learning material, quizzes do not provide feedback, which would create a teachable moment and no longer reflect the learner's final understanding.
Quizzes are scored and reflected in the learner report. Optional settings are available so learners can retake a quiz if they don't pass above a certain score. This gives learners the opportunity to review the learning material.