When a person begins his academic career, you are responsible for their decisions and behaviors. No student may be forced to attend classes, have chosen to have a post-secondary education and are able to determine whether they should participate in a particular class.
Students are exposed to new opportunities when they start college. The university is much more than academics – clubs, sports teams, employment, etc. all very important for the lives of students. It is for each to decide how to manage their time and how to prioritize different elements of your busy life.
Certainly, when I was a student not long ago, I attended my classes all the time. This does not make you a bad person or lazy! From time to time, everyone gets sick, or who want to attend an event that conflicts with your class schedule, or if you decide that it is worth returning to class in order to perform a task on time. Learning to manage all these things is part of becoming an independent adult. For courses that are more self-directed, may be perfectly acceptable to read the documents at their own pace, rather than attend classes. Students who live off campus, in particular, may find that time is not worth the expense for a category to which the notes and slides are posted on the Internet. On a daily basis, students must weigh the opportunity cost (a concept I learned in college!) To attend a class against all other possible activities that could be done and decide for themselves what is more important.
Some courses are able to solve the problem of absenteeism from the fragmentation of hours of courses from the lectures and seminars in small groups. During college, many of my classes were several hours of lectures (with almost no interaction with students) and one hour per week in small tutorial groups each. No one would notice or care if you do not go to conferences, but the assistance is part of the vote that I received for the mentoring component of the course. Most people lack one or two tutorials a term and have managed to maintain a strong involvement of these brands. Others have chosen not to participate in exercises on a regular basis and, consequently, their marks for participation were lower. This teaches that there are consequences for their actions and they alone are responsible for their successes and failures.