Recruitment agents are people who represent employers who are trying to fulfil a role/vacancy or a new position. They complete a lot of the preparatory work such as placing advertisments, reviewing resumes and conducting potential candidate screenings. if the position is filled the recruitment company receives a fee which can be a percentage of salary or a fixed fee.
Whilst this is a time saver for employers, there is no guarantee that a suitable canididate will be found or the candidate will be a good fit for the company. In the old days, recruiters would establish long term professional relationships and place jobseekers in most of their roles throughout their career.
Often times, job seekers can get a better result if they get an opportunity to speak with employers directly from the beginning of the job search process. You may be perfect for a role however due to the recruiter's inexperience in your skill set you don't get an opportunity for an interview.
Another challenge for candidates is recruiters not reading a resume beyond the first page even though a candidate may have a great fit for a job. It's really important that you provide your most relevant information in the first couple of pages of your resume to catch people's attention. Read the job tips article if you're starting your new job search.
If you're not having much success with recruiters, try and focus on jobs being advertised by employers directly or go directly to their websites and look for their careers page.