Indeed. Insurance companies, whether you agree with them on the specific criteria they choose to evaluate what they will pay for or not, do tend to have this nasty (for quacks, anyway) tendency to require some evidence of efficacy before they will pay for a treatment, all from a desire to minimize cost and maximize profits. On the other hand, the chiropracters' desire may not be that misguided for two reasons. First, if enough patients want it, insurance companies will often pay for a treatment, even if evidence from well-designed clinical trials for its efficacy is lacking, such as vertebroplasty or, back in the 1990's, bone marrow transplantation for more advanced breast cancer. Insurance companies will sometimes do this to prevent the loss of subscribers unhappy that they won't pay for such treatments. Second, having insurance companies reimburse you for services cloaks you with the mantle of "respectability," of being part of mainstream medicine. This is invaluable, even if it does bring with it the headaches of paperwork, the insurance company dictating how much it will pay for what procedure, etc.Whatever you do, do not make the mistake that many chiropractors are making - do not try to get your services covered by insurance plans. This is the kiss of death for "alternative" practitioners. Although getting covered by health insurance plans may yield a better cash flow for the marginal "alternative" practitioner, it is a disaster in the long run.
Just look what insurance coverage did to the "real" doctors . The ones who were getting paid in chickens (when they got paid at all) did better, but the profession as a whole ended up saddled with endless paperwork and red tape. Eventually, the insurance companies ended up telling the doctors how much they would get paid for everything they did. Makes getting paid in chickens and corn look good by comparison.
Bottom line: even if you could do it - stay away from insurance companies (this includes the biggest insurer of them all - the Government). You don't need that kind of scrutiny and you surely can do without the paperwork. After all, if you wanted to fill out forms, you would have become an accountant.
If any of your "clients" ask why you don't accept insurance, there are a number of good answers you can give:
 "The insurance companies are a part of the conspiracy to keep people sick - I'm trying to keep people well."
 "My therapies are too much on the cutting edge - insurance companies still call them 'experimental'"
 "Insurance company policies are too regimented - I treat my patients as individuals."
Or you can think up something that fits your particular style of business.
Finally, of course, Prometheus insists that you emphasize these three points:
 All the doctors they have seen in the past were incompetent (they may have already told you this) [Orac's note: I'm not sure I like this one...]
 You know exactly what is wrong with them - and it's not due to anything they did, like smoking or overeating. Blaming the government or large multinational corporations can be useful at this juncture. [Orac's note: This one is absolutely key. Quacks have to convince their marks that they are somehow "poisoned" and that it is not their fault. Blaming mercury in vaccines or from amalgams is a good example of this ploy. Using various "liver flushes" and enemas are other examples of treatments based on ridding the body of undefined "toxins."]
 You are the only person (or one of a select few) who can cure them (or at least return them to health and the need for a life-long maintenance program).