This is my thought too. Too much of “real” modern medicine is simply prescribing big pharma’s pill-du-jour for what ails you, and if it doesn’t work, try the next one. Much of the time muscle and joint pain needs physical therapy. Chiropractors who provide that can often provide relief even if they don’t cure the underlying problem. However, when they try to, for example, treat a sciatic nerve inflammation with manipulation like I saw with one acquaintance, the result will be the opposite of good.
To be fair, many people nowadays don’t want ongoing therapy, they want a magic pill. (Real) Doctors often don’t have time to do in-depth diagnoses, particularly for minor ailments. Chiropractors, physical therapists and professional masseuses often provide the necessary but non-pharmaceutical relief treatment doctors aren’t really there to perform.
From what little I know, a lot of chiropractic thought is tied into weird 1800’s misapprehensions about the human body not a lot different than reflexology, phrenology, aromatherapy and Freudian analysis. I suspect that chiropractic survived because the physical therapy part provided some relief, just as Freudian woo survived because it at least got the messed up patient talking about their problems.