I've worked at, hired at, and consulted at many companies. I've never once seen an HR department be incentivized to interview people just for the sake of interviewing. At my last two companies, recruiters are measured on the number of candidates that end up being extended an offer, and are negatively measured against the number of candidates that are rejected. If a recruiter is pulling in a large number of people that all get rejected, that's not due diligence, it's wasting everyone's time and is a signal that the recruiter is not very good at identifying suitable candidates.

>HR metrics are all based around pipelines, just like sales people. They get measured on number of candidates interviewed, and the more candidates interviewed for a specific position the better, as it makes them appear to be doing more 'due diligence'.

Wait, is this really a widely prevalent practice? Any stats/data?

The primary criteria at my company is retention. Once the HR forwards the resume, the interview only moves forward if the hiring manager is interested in the candidate. The hiring manager wont waste their time with multiple interviews when they know for sure that they're going to reject the candidate. What purpose would that serve?