Because, ayg, they have not only milked it and milked it, but they have discredited and contradicted every scrap of reliable evidence that may show their daughter to be dead. They are doctors, yet they offered the most ridiculous reasons why firm forensic evidence ought to be discounted - I'm no medical bod, but even I can see how childish their responses are. They've changed their statements quite radically on numerous occasions and their cronies, when they have spoken, have been suspiciously evasive. In short, their behaviour has hardly been the usual behaviour of parents in such circumstances. That they are highly articulate doctors, he an eminent surgeon and both 'devout' catholics, they have played to their advantage.
I suggest you read this:
http://www.scribd.com...Cann-Was-Not-Abducted . Before you tell me it's some kind of conspiracy scare story, bear in mind that the author's sources are all verifiable and reliable.
I really do hope the child is alive and well, but I have difficulty believing it. Somehow, I think the McCanns do too.