Because Exton had been threatened with legal action if he shared the information with anyone. OG had to get the McCann's permission therefore.
So if Exton were bound in law not to share the information why did the McCanns give permission for the e-fits to be released if they were so damning? How did the police even know of their existence in the first place? did the police specifically ask for the e-fits but weren't interested in any of the other information that Exton had gathered? Why, having received the e-fits which some consider so vitally relevant, did the police eventually go on to re-open an investigation into stranger abduction do you think?
You have still failed to address the rest of my post. The McCanns were under no obligation to set up a fund to investigate their own crimes, yet according to some that is precisely what they did. Do you think this is credible behaviour? If they realised that any donations could only be used for the purposes of investigating a crime they themselves had committed (otherwise people would raise an eyebrow), they could simply have handed over any donations to a missing persons charity (as they were so frequently chastised for not doing so by their detractors), claiming early on that they had come to terms with the fact that Madeleine was not coming back, then slinking off into the shadows, and not bothered to write a million pound book to fund yet more investigations into their own crimes. Let's at least acknowledge that such actions, if true, are incredibly bizarre and unprecedented in the history of similar such crimes.