And that would be great, if only we lived in a world where everyone was judged purely on technical merit and experience. In reality, social integration with the existing team is exceptionally important. I really wouldn't expect this to change any time soon.
Why assume that selecting candidates for interview based on the results of a blind audition/technical challenge approach like the GapJumpers model wouldn't also yield fantastic candidates who fit into the culture? The real benefit is increasing the diversity of who you interview in the first place, since getting the interview is usually the hardest part. Since there is so much bias associated with reviewing résumés then the entire process is tainted. At least if you eliminate in the first step you have a chance of eliminating it at the next steps as well.