Although they don't go to Medical school, those are MD's they go to Chiro school and Become DC's. Just like orthopedic doctors are often DO's don't study medicine solely as they typically treat with surgery.
Most people who go to standard medical schools are bitter about Chiro's because you can get in and out in less than 7 years and make a $hit load of money. Plus you don't have to do round's and a residency.
Most people just associate Dr with Surgery, not the case a typical MD wouldn't be allowed to touch you with more than a needle unless of course he had to give an emergency trach on the side of the highway.
I don't want to be a dick here, but you are so far off it isn't funny.
1. Orthopedic docs are not often DOs. Orthopedic surgery is one of the most competitive medical specialties out there. You have to be near the very top of your class to be an orthopedic surgeon these days. 99.9% of DOs could never make it into an MD orthopedic surgery residency program. That there exist any DOs in orthopedic surgery at all is due largely to the fact that they have their own special DO residency programs.
2. Nobody in med school is bitter about not being a chiropractor. Anyone in medical school right now could easily, easily have made it into chiropractory school. Also, the average salary of chiropractors is nowhere near the average salary of real doctors. The average salary for a chiropractor is 80-90k, while that of an MD is around 200k (with the average for specialists being considerably higher). And, look, I'm not trying to be a homer here, by the way. If you had said dentist, then I think there probably are a certain fraction of doctors, particularly those not in the high-paying specialties, who probably regret choosing medicine over dentistry. But trust me, none of us envy chiropractors.
3. Regarding your point about surgeons and trachs, technically once you are a physician, you can legally do any procedure you want. You don't have to be board-certified in dermatology, for example, to inject botox. Board certification just makes it easier to get a job in a particular field. But you can theoretically work as any kind of doctor you want, even if you didn't complete a residency in that field. (but good luck getting insurance companies to pay you).