It's still slave labor if the most basic of comforts and privileges are locked away from you if you don't participate.

Plus you don't really have choice in the labor you perform, no choice in where you perform it, no choice in when, you aren't really paid, you can only spend money in the commissary (at insanely inflated prices).

Sure it's not a slave on a cotton field getting whipped for not meeting quota, but it really isn't far from that.