Many recruitment companies in today's competitive environment are specialists in their field, whether it be engineering, sales, executive, office support, etc. Sometimes, applicants have a skill set that, under normal circumstances, cannot be utilised by the consulting company. Rather than giving the applicant a sense of 'false hope' that the recruiter is sourcing employment on their behalf, the recruiter will inform the applicant that their details have not been retained. Sometimes, the recruiter may return the resume to the applicant so it can be re-used for another application. If you are unsure whether your resume has been retained for future opportunities, ask the consultant.
Potential employers use recruitment companies for many reasons.
One of the most cited reasons for a company to use the services of a professional recruiter is so they do not have to wade through hundreds of applications as well as unsolicited candidates approaching them. Approaching a company directly will almost certainly do much more harm to the chances of gaining employment than enhancing them. One of the most difficult things to do in any job is negotiate your conditions such as salary package, benefits, etc. These things are particularly difficult when you are dealing with a new potential employer, it is certainly a nerve racking time. Recruitment consultants take some of that stress and worry away from you.