Consider another scenario. The person responsible for screening waits five days before beginning to review 140 resumes. Suppose your resume is somewhere near the bottom of the pile. On the subject of recruiters there is a range of possibilities. A recruiter I know who specializes in civil engineers told me he receives 100 or more unsolicited resumes a week.
Most firms consist of a couple of people with minimum staff support.
Therefore, they rarely have the time to review every resume that comes across their desk. Furthermore, updating their files can be very time consuming. Chances are that you have been contacted by a recruiter in the past. Recruiters are networking experts. If you had contact with a recruiter in the past, he may have called you about a particular job he had in mind.