[bstpierre]

Another perspective is that interviews can also be about avoiding anyone that might be a bad developer. If you have a large pool of applicants, it's "safe" to basically reject by default and only proceed with a select few who seem like the best (along whatever axis is important). You might miss out on a really good employee, but you're also less likely to be saddled with someone terrible. The downside risk is worse than the upside risk.