I do this to encourage attendance. Before I ever implemented this policy I did a statistical analysis of several hundred of my students and found that good attendance correlated strongly with good grades. I hope that this is because my lectures are good, but in case it isn't, I don't want to penalize students who are able to learn the material without coming to class. Therefore students with poor attendance receive no grade penalty ; they simply don't get a bonus. (The grade cutoffs on the 1000-point scale will be decided without regard to attendance.) This is fair: if you think you can learn the material without coming to class, I simply ask that you prove it to me on homework and exams.
Also, students who come to class regularly are exposed to more material than I can test (final exams would have to be far longer than two hours to be truly comprehensive). The bonus additionally reflects my belief that these students have learned more than students who missed classes but still did equally well on exams.
Example: Early in the semester you miss a class to study for an exam in another class, or to go home to see your family. Later in the semester an illness or family emergency requires you to miss two more classes. Because you now have three absences, one of which is unexcused, you are ineligible for the 25-point attendance bonus.
At the moment, Homecoming is not listed as an official holiday this year; I don't know if this will change.