Reasons for not using a recruiter
First and foremost: The majority of recruiters do a horrible job focussed just on money. They don't (seem to) care about the people they represent and the companies they represent, their only focus is the bonus they get out of it. They create a really toxic environment for jobseekers as well as companies with job openings. The fact that these days you can't even use Google in a simple way to look for a job without finding dozens of recruiter websites is enough proof of that. Now if they were doing a good job finding matches, that would be OK, but in a lot of situations they lie, twist, hide the truth and misrepresent developers and companies. Using recruiters to find a job keeps this toxic environment alive. This alone should be enough reason to not use recruiters.
Keep the above in mind also for yourself and your image towards potential employers. I've heard of numerous situations where after a very nice job interview that was positive from both sides, either the developer or the employer got the message "yeah, the developer just isn't interested" or "the company is not interested in hiring you", while there was a clear interest. The reason they say there is no interest is because in the negotiations for the recruiter fee, the recruiter didn't feel like they got enough money, so they lied to both parties. After a good interview, this reflects really bad on you. Based on an interview, your potential employer can get certain expectations, and when they hear you're not interested (or worse yet, when they hear you think they offer way too little salary while you don't actually think that) this reflects poorly on you.
Many recruiters are known for their bad business practices. I once went to an interview for a company that was really excited I was interested in working for them, because my CV was the perfect match for their job! We had a really good interview, up until the point where they asked me what kind of C++ projects I had done. I was confused. I had never done any C++, and surely this was not on my CV. "Well, your CV here lists you with a couple of years of C++ experience". The recruiter had altered my CV to include experience I didn't have to make me a better match, in the hopes of it not being noticed.
Another good example is the recruiter that I accepted on my LinkedIn. A couple of days later, I got several messages from people I know asking me why I recommended them for another job. I was confused. I did no such thing. It turned out that the recruiter was just going through my LinkedIn network, calling everyone he could find a phonenumber for telling them that I had "recommended them for this position" that he was trying to fill. I was pissed, and ever since then I do not accept LinkedIn requests from recruiters anymore.
And then of course there's the recruiters that misrepresent themselves. The best example must be the guy that started a new meetup group in Amsterdam for PHP developers, and signed all his e-mails with him being the "Amsterdam PHP Community Manager". Of course it was just a coincidence that there was actually an AmsterdamPHP (note the absence of a space here) meetup group as well, a quite popular group. Even after being told that this group existed, he kept on using this title for quite some time, purposefully trying to scam his way into the lives of PHP developers.
Long story short: The chance of you being misrepresented by a recruiter is huge and this may reflect badly on your image towards fellow developers as well as potential employers.