I've got forced military service, but my country ain't at war, so I've just gotta work 6 months in shitty jobs, that are necessary for society for free. Oh, and your free time in the barracks consists of drinking beer, playing cards and smoking
The ruling class needs workers to work in order to exploit them.
This doesn't mean all work is intrinsically serving the ruling class. But in a society set up to funnel as much money as possible to its rulers, then it does.