in the previous expansion, i did not see this that often, most of the settlers was escorted, but some where taken by barbarians still and at times, you saw one moving alone, but it would almost never reach its location.
in this expansion, there is way more settlers moving alone then before and barbarians do seem to ignore the most of these, but some are taken, but not as many as before, as i see lots of camps which show no signs of captured settlers nor workers, while in the last expansion, you would often see some captives in most camps.
i hope they get this fixed, as its annoing to see ai settler moving to a good location, just because the barbarians ignore them, could understand it, if they reached this place, with Escort which managed to defend the settler on the trip.