I was in recruitment for 8 years or so, it's a thankless job from both sides, clients whinging about the cost of paying for exactly the candidate they asked you to find and candidates whinging that YOU didn't get them the job.
I've helped quite a few people get pay increases of 50% + over the years, many people have said I found them their dream role and I've had clients tell me they were over the moon with the people I had found to fill their vacancies. The reason I stopped is that for every decent recruiter there are 100 cocks and you get tarred with the same brush, it gets annoying. As for candidates thinking I should rely on their CV for the facts, yeah good one, part of the job is interviewing the candidates in depth on behalf of the client, anyone who won't do an interview with me doesn't get put forward. And as for no relevant skills, well run competency based interviews meant I didn't have to know everything my candidates did but I did need them to prove they could do what they said they could.
I often worked retained as why the hell would I work for a month on a brief only to have the role cancelled at a whim or some such and find myself out of pocket. Ask for 15k up front and you soon weed out the timewasters.