Advocates of Medicare for All, such as Senator Bernie Sanders, would have you believe that Americans are overwhelmingly displeased with the status quo. In fact, the opposite is true; a majority of Americans are happy with the quality of care they receive. Additionally, most Americans would like to keep their doctor, and the choice they currently enjoy in deciding who provides the care. Under a Medicare for All system, that choice would be taken away.
While a higher number of Americans are concerned about costs, they do not seem dissatisfied with the quality of the current system. Therefore, a complete restructuring of the United States' healthcare infrastructure seems excessive and undesirable.
Considering many are happy with their current private healthcare plans, forcing them to change to a single healthcare provider would likely be unpopular.
Smaller changes to the current system would be favorable to the complete restructuring that Medicare for All would create.