I would think it's because they are unsure, and in their unsuredness, need to reinforce the same onto anyone who will listen.
Once you know the truth, nothing will ever replace it.
Marxism tries to do the same. It is the lying to ones' self that the master of lies loves the most.
Fortunately, when one finds Truth, there is no going back to the father of lies...and there is the true gnashing of teeth....Poor satan...he lost before he began.
FMCDH(BITS)
Good point as well!