Class attendance shouldn't be a portion of your grade. In the majority of my courses attendance is taken daily and factored in to your final grade, and in most cases missing a certain number of class days results in dropping your grade a portion of a letter. There are often circumstances that don't fall in to the "excused absence" category that may cause a student to miss a class. Instances such as; studying for another classes exam, feeling under the weather but didn't go to the doctors office, another obligation, etc. all would result in a grade deduction in my classes that take attendance. I also feel this isn't the right way to get students to attend class, professors should make the material and class intriguing enough where students want to show up to class, and at the end of the day we are paying for these courses so I think the decision to go should be your choice to make.