As with all professions, you're going to have people that are legit and you'll have the people who aren't. I'm somewhat in agreement with you that chiropractors can be a hoax. That's not to suggest that all are or that some may not be experts at easing tension that people have. Most people I know that go to chiropractors are either fat and have poor sleep habits (sleeping in weird positions because they're fat) or one lady's had major neck trauma. She's had maybe 3-4 neck surgeries and has chiro work done on her mid-upper back to relieve tension. She probably weighs 120lbs and is in her 50s....in good shape, just dealing with some major pain issues and doesn't want to take meds.
In 1995, my aunt lived in Tokyo and dated a Japanese man who studied it...the Japanese take it very seriously. I suppose it's got some Eastern medicine flair, but can be legitimate if someone is sporting real injuries. My lower back got screwed up in 2002. I went to a PT and did exercises, various treatments, and ultimately my back healed up. I re-injur it annually, but have never been to a chiro...always considered it, but never believed in what they do or that they could help me. My issues are REAL issues that can't be relieved with anything other than time/healing, steroid treatments, or improved muscle conditioning. When I was running 60-100 miles monthly, I didn't have back problems as much. Running 8+ miles weekly kept my problems at bay. My lower back issues are caused by poor muscle condition and core issues with my vertebrae that back-cracking won't fix. The poor muscle condition is a result of me having a desk job and the only way I can work those muscles is by running or snowboarding or doing activities that force me to move in ways I don't normally move.
A few Chiros around here offer massage...which is part of their scam to get people in the door. They sign people on as patients and have health insurance cover massage therapy at a more expensive rate than what a typical massage would cost. This is all about turning a profit....especially if the patient pays only a co-pay and the insurance is stuck with the majority of the bill. People just want attention and if they're only dropping $15-25 per treatment to get petted on, they're willing to do it.