You can regard it as another form of extreme exploitation - if that makes you feel any better. But (to take a good example) consider the hundreds of workers building the Ribblehead railway viaduct in the early 1870s, while living in a hutted encampment miles from any adequate source of supply. The contractors had to keep them fed, and maybe more essentially, 'watered', so the work could continue. What would be an better arrangement ? (The watering of course mostly consisted of weak beer, with predictable consequences). There had to be a currency of some kind, hence the truck system.