It's not so much a case of "if you don't know anybody you won't get on"... It's more of a case where we have a stack of resumes a foot high. How do you reduce it to a more manageable stack? You go first for the resumes with good recommendations from the guys who already work here and have good things to say about guys they think will fit in well.
Some Airlines do the same thing with a University Degree, or time on type...
If you have two qualified candidates, one an unknown, one recommended by several guys who already work for you, who would you hire?
We are going to hire 100+ guys this year. That stack will look pretty short.
Cheers.