I don't know who came up with the idea of the "excused absence," but it's a terrible idea, and here's why. You want students to show up to class because they are supposedly actually learning something by being there. If they miss class, from an educational perspective, it doesn't matter why; it only matters that they've lost 50 minutes of instruction.
The "excused absence" confuses the issue by making it, in essence, a moral one. It makes students believe that being absent for a good reason is the moral equivalent of being in class.
Well, on a moral level, maybe it is! But why is there a moral level to attendance policies at all? College students can vote. Can't they also judge the impact on their grades and decide, as adults, whether to show up to class if they're sick, if they're feeling a little miserable, if it's an absolutely beautiful spring day?
One thing I never want to do is make judgment calls about whose absence is morally righteous and whose isn't. That isn't my job. More to the point, it doesn't matter. You're in class or you aren't, and a student's goodness as a person isn't a factor.