When I was in college, I used to do this very job working at a Walmart distribution center. There were dozens of people working every shift that did this job. And most of the trucks were like the one in this video - a hodgepodge stack of different box sizes.
It's not a very fun job, truth be told, but I think it paid a lot of bills for a lot of people. Raising the minimum wage probably alters the economics of unskilled labor enough that there stops being an economic justification for paying human beings to do work that can be done less expensively by a robot.