While there have been a lot of replied I think the main reason 5) is not legal is because it is much more likely that a driver will do this 12h a day for 6-7 days a week.
So he will spend more hours on the road which is more demanding for him as well as his car, which is why it requires more regulation.
So he will spend more hours on the road which is more demanding for him as well as his car, which is why it requires more regulation.