Our school is just starting to crack down on absentee notes as well. And making a point of kids being off school for a legitimate reason. And fair enough.

Its more for people who just don't think education is important. A family member of mine keeps her DD home when hung over. Because she either can't be bothered getting up, or she needs help with the younger one Others in town take theirs away for 6 weeks every year for work. Weather or not they take work with them I don't know, but if they do I seriously doubt it actually covers the whole 6 weeks they'd do at school.
Others do random shopping trips or to catch up with family & friends in the city through out the term, often for close to a week 3 or 4 times in a term.

I only mention these people, because I am close to these people. I know their circumstances & I know they really should put their kids education over some of these things.

Honestly, one week out of the year for a holiday isn't such a huge thing. If it was one week out of every term, it might make a difference. I wouldn't worry about justifying it myself. But I'm pretty sure if SIL had to justify her hang over, she'd say DD was sick...