i think, due to having failed their child completely as parents, the McCanns think that by filling the papers with all the efforts the family are making to find her people will just start assuming they're a great and caring family who would never have neglected their child. It means there's no space in the papers for anyone to be talking about what a nice little girl she is, only what great people the family are for trying to find their child after they've lost her.
I don't want to demonise them, no person should have to experience the completely unbearable pain I imagine they feel, I do have sympathy for them, I know it was one terrible mistake that they have to live with but I think they should at least realise and accept the mistake they made rather than insisting what great, caring parents they are and trying to prove it with a world tour.