Originally Posted by
coffeecake
My guess would be that they're avoiding political interpretations, since the ramifications of recent events are still unfolding.
My high school US history class could have probably made it up to Ronald Reagan (the present) at the pace we were going but wrapped it up at just before Watergate, it seemed, to avoid kids bringing stories home to their parents and getting teachers in trouble on a hotbed issue. Still, even Vietnam we could review at the HS level from old Doonesbury books.