They can, just not alone. If they were to unionize in sufficient numbers, there would be nothing to do but meet the demands. But “unions are bad” is the prevailing belief in the US, not to mention the huge amount of efforts that companies and the government go through to suppress them.
Many physicians still work in sole proprietorships or partnerships. From an employment perspective they are management, not labor.
Some physicians working as employees of large provider organizations are unionized. The government doesn't do anything to suppress this. Rather the opposite.
