Why Piano Competitions Will Never Yield a Superstar

Thanks to Alvaro Mendizabal for finding this.
I have been opposed to competitions for some time, having said that they are for horses, not musicians (actually they are probably not even good for horses). 
However, the atmosphere at GFA did not seem overly strained even though there were 4 competitions happening. I do know there were issues and also a limited programme choice and some controversy afterwards. Are competitions mainly for the benefit of the organisers? Getting more publicity and funding for them?
Competitions don’t seem to have been harmful to the careers of Johannes Moller, Zoran Dukics, Denis Azabagic, Manuel Barrueco and David Russell. But would these artists would have made great careers and wonderful music even without winning anything (John Williams never entered for competitions, neither did Bream, or Segovia!).

What do you think?