You could ask the same question about the Madeline McCann case. She wasn't the only child to go missing (and still not be found).
I wonder what makes specific cases of significantly greater interest to the media?
The media are infested with upper middle class snobs on the whole is why. If Kylie from Ancoats was on the piss with her mates on holiday and left her three kids unattended and one went missing, the media would have slaughtered her. She would have been prosecuted and her other kids subject to a protection order at least. Two middle class doctors? Different story.
Similar with this case. Good looking woman, seemingly picture book perfect life suddenly disappears into thin air, great story to sell their papers.