Because sometimes the government can use its powers for the good of the general public, even if it negatively effects business. How negatively Tesla would be impacted is debatable - I don't think anyone would expect them to be forced to let people use their chargers for free.

I dont think people would put up with a gas station that only fueled Toyotas, or a parking lot that only allowed Fords. This doesnt strike me as being terribly different.