I would suggest one reason that's not the case for physicians is because we, on the whole, are actually pretty good at policing ourselves and dealing with misconduct. We have state medical boards that can act on licenses, we have facility credentialing committees, we conduct peer review, we have remediation programs for doctors with problems ranging from technical issues to substance abuse. We carry individual malpractice insurance, which can get expensive or be denied outright if an individual demonstrates a pattern of practice outside the standard of care. There's no powerful "doctor union" and no blanket qualified immunity. In short, we're professionals in a profession that is charged with caring for other people. It's not a perfect system obviously, but it basically works and the public generally sees that it works.
The police don't have any of that. No licensing, no insurance, no regulatory boards, their "peer review" is a rubber stamp joke, they're largely immune to consequences of misconduct and incompetence, and to top it all off, they've been told they're Warriors fighting the good fight in the War On Drugs and the War On Crime. They're about four steps removed from calling in airstrikes to support no-knock warrants.
A person who goes to a doctor (voluntarily) and doesn't like the doctor can just go to another doctor. We don't get to choose which police officers come to us (typically involuntarily).
The police : physician analogy is not a good one. The professions couldn't be more different in their attitudes toward quality control and self-regulation.