A typical scenario: a person sustained an injury in an auto-accident. At first, that injury might not seem or feel to be very serious, but the injured still wishes to get medical care. He gets one of his friends to refer him to a local Chiropractor who treats him for a 3-5 months without referring the patient to other specialists.
This kind of treatment history will necessarily reduce the recovery. I work with some great Chiropractors in San Francisco and Sacramento areas who do a great job for a very reasonable rates for their patients, many of whom are recovering from serious injury accidents. However, I am also aware of the general perception of Chiropractic professional in the community. And the insurance companies are aware of this skeptical perception as well. They know, that the opinion of a Chiropractor is not nearly as credible as that of an a medical doctor. Further, a successful argument can be made by the defense that if an injured person only sought treatment from a chiropractor, this means that he/she wasn't injured seriously; otherwise he would further treatment elsewhere.
Even more importantly, not having a thorough medical examination with an M.D. or an orthopedic surgeon may aggravate a very serious injury (injury to discus, vertebrae, etc...) and make the recovery much slower and painful if not diagnosed and addressed properly.
Thus, it is very important that you see your primary physician at least once and discuss referral to an orthopedic specialist or another doctor who can take your x-rays and examine your injuries more thoroughly for possible disc protrusions/bulges, lacerations, fractures, and other injuries that might not cause as much pain at first, but the ones that tend to also exacerbate with time, if not treated promptly.