Getting either one of shipping lanes or trading routes set up is pretty much a must on longer quests, or ones with only small amounts of gold on the map, but the problem with getting both AND a high villager count, is that you start cutting too much into army supply, and so merchant transports, followed by caravans get the chop first, at times when people want to field bigger armies, or don't want to get to an ultra late farm+caravan+shipping eco (because if there is any resources on the map, it's more efficent and easier to set up to take them, unless the ai is keeping you in your base like a stronger PvP player)