You've been extremely lucky. It may well vary by niche, but certainly I've experienced or know someone that's experienced almost everything listed here and more.
Not all recruiters are scum but a lot are. My top warning signs:
Recruiter talks about their honesty or integrity or years of experience. This is a massive red flag. They're lying about their honesty and integrity. Walk away.
Recruiter asks about other people in department, talks up a job, you apply then your more senior colleague gets a call about the same job you supposedly applied for. Of course, the whole thing was just to get the more senior guy's CV. There wasn't even a job.
Threats of legal action for not taking a job.
Non-payment for contract positions where payment has to go through the recruiter (I know of 3 or 4 guys who took the same company to court for non-payment).
Ridiculous unenforceable terms and conditions in a contract ("Contractor will not talk to client about future projects" - so no planning and no delivery then?)
The recruiter is young (early 20s) - they're normally put in a sink or swim environment that encourages this type of behaviour. The guys that have been around for between 5 and 10 years have learnt what works and more importantly, what doesn't. Anyone claiming 20 years in recruiting is probably either psychologically unbalanced or lying. Would you still be hitting the streets in a job like that after 20 years, or would you be management by then?