I've been part of different hiring processes long enough to see just how many people get hired because they know somebody on the team, when there were other candidates who were as qualified or more qualified. When we can hire 1 person, my experience is that it is 1000% biased towards knowing somebody. Sure, if there is an undefined number of open reqs, you can argue that there is still space for the more qualified, unconnected applicants. But when you're dealing with a finite number of open reqs, there's actually not, and it is a zero sum game.