Fun fact: it was helpful for a hitchhiker to ask the driver for one of the blank paper discs for the tachograph. Later, when standing beside the road and waiting for another lift, you could hold that up whenever a truck approached, and truck drivers would take it as a sign that you were relatively trustworthy.
In which case, the passenger might sue the driver, and the driver might not want that, so the driver chooses to not pick up hitchhikers. One might say this is a consequence of not having taxpayer funded healthcare for everyone, since exorbitant healthcare costs + needing to find someone to milk mean everyone ends up looking out for their own ass.
Another scenario is the passenger steals the truck or its contents , in which case the insurer would say not our problem. You were covered for random acts of weather/other drivers/machine failure/thieves breaking and entering. But not if you willingly let them into the truck. Seems like a reasonable caveat.
It's also worth noting that a lot of the culture around the labor market is different as the European regulators tend to be a bit more of an aggressive stance on companies creating pressures on employees and then try to shift all blame when those pressure's lead to rule breaking and accidents.