I think that the short hand of "this person vouches for this other person" is a good enough basis for a lot of pre-screening criteria. Not that it makes the person a shoe in for the job, but it's enough to say that you can go by on a referral. 

You might say, this is a strange way to pick people, but this is how governments interview people for national security roles. They check references. They ask questions. 

I imagine more questions would be asked to the third party who is 'personally referring' the applicant, leading to a slightly different series of interviews anyway. In my experience, people have to work a lot harder to get a job, than to keep one. I know that it's true with everyone that referred me to just about every position. Then if I perform badly it looks poorly on them, but after a certain time, I'm the one referring people onwards, so I have to make my own assessment of if I'm willing to put my reputation on the line.