It comes from risk aversion. Firing people is painful and expensive. And it's hard to know how good someone actually is just from interviewing. So if I've wo

It comes from risk aversion. Firing people is painful and expensive. And it's hard to know how good someone actually is just from interviewing. So if I've worked with someone previously and know they're not lazy or incompetent, that's worth a ton -- even if they're not the absolute best person for the job.