The other 'nail in the coffin' factor is that editorial photography must be true to life to be sold as photojournalism ( in this case newspapers, magazines, celebrity gossip websites) otherwise the photographer or publisher could get sued.
E.G. if a retoucher added a cigarette to a pic of Britney Spears with a baby to make up a story about her being a bad mum, she might learn of the photo, know it's been doctored and sue the publishers for defamation of character. Likewise, if Bowie learnt of these photos and they were (miraculously) retouched he could also sue the relevant publishers for printing lies about himself.
The photographer would have to produce the original raw files with exif data (date, aperture shutter speed info) from his camera, showing that they weren't doctored to avoid being sued. Raw files as captured by the camera are like negatives, can't be retouched, so are admissible as evidence.