To remove any excuse for not knowing the Old Testament.
Except for the parts about smashing heads and slaying people. The Church is more comfortable with a little popular ignorance in those areas.
Ironically, at the same time there were increased readings from the Old Testament, the Old Testament saints got taken out of the main saint calendars. Though you can still celebrate their feasts if you feel like it. Personally, I feel that we need to spend a lot more time celebrating St. Job.
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