A primary purpose of the 13th amendment is the preservation of slave labor through prison.
To call "preservation of slave labor through prison" a "primary purpose" of the 13th amendment is just insane. Sentencing people to hard labor for certain crimes had been done for thousands of years by that point. The prison carve out was a reflection of the fact that the states passing the amendment were interested in getting rid of commercial slavery as it existed in the south, not throwing a wrench into their own…
The government version of "slavery for me but not for thee"