Full-time internal recruiters are rarely financially incentivised per hire or to hit targets. If they are, I'd strongly argue that the company employing them is utilising the recruiter incorrectly.
External recruiters live and die by their targets and their commission. Money is a terrible incentive (possibly the worst) for encouraging recruiters to actually help their candidates or clients.
Just like the best engineers/designers/etc, the best recruiters are those that go above and beyond simply to help their company succeed. When you use an external recruiter, that company is an agency.