The motivations differ. Sometimes it's political, sometimes strictly economic. But it does happen.
Despite America's lack of labor protections, its doctors' presumption that they are professionals, not workers, and a dispersed industry where no one has great market share, a slow motion strike may in fact be underway here.
But it goes beyond this. Aren't doctors who abuse the payment system really committing a strike-like action for higher pay? Or those who skirt the law, making promises their medicines can't meet, for private patients who will pay full freight. Might that be a form of protest?
Even some of the resistance to Electronic Medical Records (EMRs) is, in many ways, a temper tantrum, a strike action. Hating paperwork, knowing computers can reduce the load, but being unwilling to move forward -- disgruntled labor.
One of the more controversial statements I write anywhere is that labor unions are inherently conservative. They resist automation, they resist change, they resist anything they say might threaten their members' status quo.
Family doctors are an unorganized labor union, and if they ever get together we're all in for a shock.