I used to think I was too cool and progressive to give quizzes. But a quiz tells you whether students are learning what you think you are teaching them, quickly and precisely. It’s a perfect data-collection tool: If students learned what you wanted them to learn, they will answer the questions correctly. If they haven’t, they won’t, allowing you to provide targeted help to specific students based on which questions they get wrong.
The only caveat is that you shouldn’t grade the quiz, because attaching a grade to a quiz ruins your data.