After reading those 400 pages that were released, it became obvious from Cindy Anthony's conversation with the friend Ryan, and then with Amy that Cindy has known for quite awhile that her daughter lies about everything. It is also obvious that Cindy did not trust Casey to care for Caylee on her own, outside of their house. Cindy called her daughter a thief, a sociapath(to Ryan), stole from her grandmother(Cindy's mother), and she could not be trusted.
This to me, means they (the parents) have known for a very long time that their daughter was not right and needed help. George and Cindy Anthony made the decision long before this current situation to either ignore, placate, coddle, and not get any professional help for their daughter. I am not sure if this was done for the good old Southern reason of not looking bad to the neighbors, but whatever was done, or not done did not work, and many people are now suffering for it.
If they believe that Caylee is dead, and that was her body in the trunk, they would also have to believe that Casey is involved somehow. It would crash their world down. They have been living in denial for a very long time. When the truth is laid before them, it will break them. Cindy Anthony is cracking already.