Most companies understandably don't like publishing a salary so the recruiter acts a filter on both sides.

I'm a hiring manager and having a firehose of applicants would fill me with dread. My company has tried various "hacker" recruitment sites and they are all terrible - in terms of candidates and the supposed tests they use to rank applicants.

Recruiters are expensive but so is my time, they are very much a necessary evil for the foreseeable future.