They went to save a caravan, didn't they? I get the impression the town they are now in is the only friendly place in the tower, and it's probably at the bottom. So, when you leave the town and start to climb, you'll just encounter monsters. And likely the higher you climb, the tougher the monsters. The patrol is probably just keeping the perimeter of the town itself clear but obviously even the road to the town from the outside of the tower can be perilous, or maybe the caravan was transferring some sort of a resource to the town from elsewhere in the tower.