Sometimes treatment decisions are made strictly on the basis of finances. If you have insurance that only covers a medical doctor for the treatment of back pain, then that's who you go see.
For some people it depends on who's available. If it takes three months to get in to see the doctor but the chiropractor can see the person today, the patient gets chiropractic care.
A study was done recently of over 100,000 patients. All had coverage for both medical and alternative care. About half the group went to a conventional care provider (doctor, physical therapist, nurse). The other half saw an alternative specialist. Alternative care included chiropractors, massage therapists, and acupuncturists.
Differences were seen in gender and geographic location. For example, men in rural towns were more likely to see a chiropractor. Patients who were cared for by alternative specialists were usually healthier. They had fewer other problems.