I wondered this as well. Sometimes, I think, MOO, they are working very closely with the FBI, with their attorney, of course.
After all, for now, their son is missing for too long, now. And yes, there is ONE indictment, but their son is missing. I would be a basket case.
I wonder if they sacrificed their reputation, agreed to be completely villianized by the public, by remaining silent UPON REQUEST just to help find their son. (Please remember, they WERE going to have a press conference and called it off because the FBI asked them to). I can't even imagine. Again MOO and all that.