They spend too much time sorting resumes. The typical explanation for why HR recruiters have no time to recruit actively is that they have too many resumes to sort. Instead, solicit the right people through good contacts , starting with people in the department you recruit for. Get out there and get active in the community you recruit from. They let managers get away with murder.
Managers hate to recruit.
But a manager's first job is to find and hire great people. Move your desk out of the HR office and into the department you recruit for. That's how you can daily influence the hiring manager's recruiting activities. They waste candidates' time. Good candidates don't have time for applications, tests and screening interviews before they talk with the hiring manager.