Opposition to Medicare for All is for the same reason. The boss loves having the power of life and death over you so that you do whatever they say. A lot of libs naively thinking that M4A would be good for businesses because they only think in terms of direct benefits, like the economy is just a video game that anyone can win (and doesn't every business want to minimize cost?!?!?). They never consider economic decisions with Game Theory or anything that actually takes human nature (i.e. long-term thinking, self-interest, SPITE).