I was totally wrong about the chests. I misunderstood when you said they were around the tower. I thought they were on the ground around the tower, as they had been. I didn’t know that the new chests had actually been put ON the tower, on that platform around the stairs. Mea culpa.
And you are right about bearers being very common from the Purge. But starting players cannot do Purges immediately. They need materials and thralls (!) and such. A named bearer that you can get from a low-level Exile camp on Siptah, for example, is quite a treasure (until you get leveled up and start getting sick of seeing the backpacks).
I don’t see how thralls let out of the cages and abandoned by players are anything but a temporary problem. In my experience, they get cut down pretty quick by enemies in the area once they respawn.
In any case, I maintain that the thrall cages are a cool idea that add a lot of flavor to the game and a bit of utility depending on the needs of the players.