Why limit the practice to pharmaceuticals? In theory the government can be a middle man for any good or service. Why not have the government buy all the cars

Why limit the practice to pharmaceuticals? In theory the government can be a middle man for any good or service. Why not have the government buy all the cars in country and the parcel them out to people at a fair rate? I think everyone (or most everyone) understands that would be a disaster. Switch the good to pharmaceuticals and suddenly it's reasonable?