The thing is, when they do that you have no idea if it’s some shitty bodyshop looking for people with pulses or a cool company that you’d love to work for, so you have no opportunity to do research into the company before dedicating time to call someone. I don’t see the benefit of bypassing their services since recruiters are usually a decent foot in the door, but maybe I’m missing something
The recruiters I've known would document their outreach to you, and notify the company that'd we'd spoken. If they'd specifically contacted me, the I bypassed them, they may still get paid somehow (but I'd lose whatever bargaining skills they might bring to the process)>.
I've talked with a number of recruiters - 2 specifically indicated that they had arrangements with the end client - essentially an exclusivity deal. Once they revealed the client name to me, they'd let the client know, and if I made contact outside the recruiter, it was still an 'introduction' they'd get paid for if/when I was hired. Both of these were from a job search in the mid 2000s.
I've spoken with many more generalist recruiters, none of whom ever indicated this sort of system. I don't think it's overly common, but it was an arrangement that 2 recruiters indicated they had. Perhaps they were extreme one-offs?