Classes should not necessitate homework in order to impart relevant information
If information is not being taught in class, then teachers are not helping students receive that information in the best way possible. Teachers are trained to deliver information effectively, and many students don't have the skills to teach or review themselves. Inversely, instead of new material, class becomes focused on homework itself.
If a teacher is not effectively communicating their content in the time allotted within the course schedule, then this is not an excuse to overwork students to compensate for their educational failings. Oftentimes, teachers will assign large chunks of information that students are forced to learn independently and then be tested on, but it is the teacher's job to make sure their students are practicing the proper learning skills. Homework is an ineffective way for teachers to measure their student’s progress.
Individual studying is part of learning, and teachers can help students process outside information when they ask questions in class. Not all course information can be communicated within the limited time frame.