It creates an incentive to grow and maintain the slave class. Instead we should be thinking rehabilitation and how to have less people in prison.
Some people might argue that we should pursue even more extreme punishments, to dissuade people from committing crimes.
So your idea exacerbates the thing you want to dissuade.
The concept is called recidivism if you are interested in corroborating or learning additional perspectives of this. And why it occurs such as the misaligned incentives that promote recidivism that we as a society can fix.
Maybe it's actually wrong?
Disagreements on values often masquerade as disagreements on facts, especially because people often use fact claims oriented to their audience’s perceived values to sell actions based on different values to them.
you're looking at this through the lens of more enforcement+penalties versus less enforcement+penalties, a false dilemma that's not what the rest of us are talking about.