Most of modern recruiting relies on the “post the job, review the applicants” model of recruiting. It works in so much as it has always worked: as a matter of convenience for the recruiter and the business, where the job could be posted and reviewed asynchronously, once a number of apps rolled in.
In a world where having a job was the most important currency, job applicants were asked to follow some basic rules: watch job boards for openings, apply as prescribed, wait days or weeks for the recruiter to go through the applicants, identifying potential candidates, treat the applicant as a complete and total stranger whose application is deeply suspect, and take 4-6 weeks to screen and interview all relevant applicants before deciding on one and offering a job to them.