Not all assessment needs to be about the learning over the entire course. Often we need to know the pattern of our students' learning during the course itself so we know what we may need to review, expand upon, or approach from a different perspective. Quizzes, even ungraded quizzes, are one vehicle many faculty use to measure not only the learning of individual students but the pattern of learning across the course.
Assessment need not wait for a quiz. There are many simple activities that can be done during the class or at the end of the class that can provide useful information to adjust instruction so students can learn more effectively.
Many of our teaching activities can be easily turned into assessment tools to give us good, immediate data on our student learning which, in turn, allows us to direct our teaching toward the identified needs.