Hey, this is Medicare. Not all doctors take it (for good reason) and the ones that do have to abide by a strict set of standards for prescribing treatment. It has nothing to do with the doctor “getting paid” to deny you treatment.
“The vast majority of non-pediatric primary care physicians (93 percent) say they accept Medicare—comparable to the share accepting private insurance (94 percent).”
https://www.kff.org/medicare/issue-brief/primary-care-physicians-accepting-medicare-a-snapshot/
The percentage is even higher for medical specialists.