I think Bart Sibrel's take on it is on point, in that it would be a bigger hit to society than finding out that 9/11 was not what they say officially.

People have a huge sense of pride attached to it, and it's hard to let go. I think the primary reason for faking it was to raise morale at the time. Younger generations are probably more open to consider it, but boomers are fully under the spell.