Do you mean to ask if Caravan guards have hard jobs? I'd say so. They have to fight off monsters and raiders while protecting some weak merchant and probably get very little time to rest.
Because everyone wants to rob the caravan, even though it's carrying mostly useless misc. items. In Fallout 1 the caravan guard job's not hard at all, you fight one random encounter with lots of backup, but in Fallout 3 and New Vegas a caravan will pretty much get wiped out if it shows up at the wrong time in the wrong place.