Barbarians stealing civilians

As of now in the game, barbarians only steal your workers and settlers to annoy you, it appears. I think the barbarians should get some kind of bonuses from taking civilians back to their camps, an increased spawn rate maybe? I wanted some ideas because as of now there's no purpose except from a gameplay standpoint for them to steal settlers and workers.

Some sort of logic would imply that if you found a city next to a barb camp and your borders engulf that camp, you get a free pop out of it