Is Incarceration The New Slavery? Does Cheap Labor Explain The U.S.'s High Incarceration Rates?

I was reading an article about Massachusetts inmates suing for minimum wage and it started me thinking. The U.S. has the highest incarceration rates in the world. We have about 2.2 million people in prison here. The shockingly high rates started a steep incline shortly after the passage of the Civil Rights Act of 1964. The Sentencing Project charts the incline:

Per the NAACP:

• African Americans now constitute nearly 1 million of the total 2.3 million incarcerated population
• African Americans are incarcerated at nearly six times the rate of whites
• Together, African American and Hispanics comprised 58% of all prisoners in 2008, even though African Americans and Hispanics make up approximately one quarter of the US population
• According to Unlocking America, if African American and Hispanics were incarcerated at the same rates of whites, today's prison and jail populations would decline by approximately 50%
• One in six black men had been incarcerated as of 2001. If current trends continue, one in three black males born today can expect to spend time in prison during his lifetime
• 1 in 100 African American women are in prison

The 13th Amendment has an exception to the abolition of slavery: “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.” The effect of this exception is that prisoners who work can be paid $1.00 an hour while working for private, for-profit companies that contract with the prison system for cheap labor. Further, private for-profit companies that run prisons in this country can get free labor for profit.

Prisoners aren't covered by the Fair Labor Standards Act and can't unionize or bargain for better wages. 

Why reform our criminal justice system when the effect is to reinstate slavery and indentured servitude on 2.2 million Americans, most of whom are minorities? Corporations exploiting this system of free and ultra-cheap labor have every incentive to make sure nothing changes, and that our rates of imprisonment keep going up. 

Wanna bet that incarceration rates would drop drastically if prisoners had to be paid minimum wage for their work? Are any elected officials concerned enough about this to do anything to reform this awful situation?