When a candidate with many years of experience is told they cannot be presented for a lower-level position, they become angry, very defensive, and often accuse the recruiter and firm of age discrimination. While it may seem like recruiters are discriminating against them for their age, that really has nothing to do with why they express concern over placing the candidate with a firm.
For the recruiter, part of developing a strong relationship with a firm is having an understanding of the type of candidate they want to see. Our job is to save them time and to present candidates who are exactly on point with their needs. Most firms give us guidelines to follow and ask us to stick to them; otherwise, we would not be providing them with a service.