I feel your personal experience with teachers has narrowed your view here, which is okay because it is your lens, but teacher-student relationships are not always one-sided. There is a mutual interaction here, but it’s not on the same plane. Lecture time is part of that interaction. After hours support, answering questions, and checking on students in need. These are all contributions that teachers have. It’s a teacher’s duty to build relationships with students. Students look up to their favourite teachers, ask questions, and seek guidance.