Retailers have kept roughly the same holiday timetable for a century. (canadianbusiness.com)
Since education systems are run by states and every state closes for the same holidays, (which are only Catholic). (religion.blogs.cnn.com)
The early church combined them because when you're making a huge cultural change, it's easier on the common folk if they get to keep their same holidays — which leads to an easier transition. (nakedpastor.com)