"Systematic reviews of controlled clinical studies of treatments used by chiropractors have found no evidence that chiropractic manipulation is effective, with the possible exception of treatment for back pain.[8] A 2011 critical evaluation of 45 systematic reviews concluded that the data included in the study "fail[ed] to demonstrate convincingly that spinal manipulation is an effective intervention for any condition."[10] Spinal manipulation may be cost-effective for sub-acute or chronic low back pain, but the results for acute low back pain were insufficient.[11] No compelling evidence exists to indicate that maintenance chiropractic care adequately prevents symptoms or diseases.[12]"
I don't think you understand the level to which people take chiropracty. People use it in a "cures what ails you" mentality. Colds, flu, hand arthritis, all sorts of diseases. There is a ton of danger in allowing "back cracking for healing" when it doesn't do anything that couldn't be done with massage.