I sort of get the criticism of chiros, because some, not all, will overinflate what their treatments can do and many want you to be a regular, as in every week. If people are finding relief, more power to them. It's cheap enough.
There is some weird stuff going on. My friend takes his kid in to treat his 'ADHD'. WTF? I am not going down that rabbit hole. A lot of chiros promote A LOT of supplements of questionable validity. Hmm, no thanks.
I've had good ones and bad ones. My last one wasn't necessarily bad, but he put me through the same exact routine every week or two. I felt a little better when I left, but like others have said, I started to equate his work with that of a massage therapist, not really essential.
When I was in high school, my spine was out of alignment and I was in pain. He took X-rays and showed me the problem, and then went to work for a few weeks to get me re-aligned. It was money well spent. I was having pain in both knees. He sized up the problem right away and referred me to a podiatrist who fixed the bad insoles in my cleats.
Every NFL team has a chiro on staff and players love it. They definitely add value, but probably cannot cure cancer. <sarcasm>