The person that wrote that is like 31 years old last week
and
"Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction."
Pretty much because the constitution has always been more of a vibe than a binding set of legal principles.
That said I think a carrot would work better than a stick here. Something like what we do to encourage military service - healthcare and college money!