The prisions are not state run but commercial entities. Thus there is a certain incentive to lobby for longer sentences in order to make more business. Occasionally they pay "commission" like in this scheme to jail youth for profit:
https://www.npr.org/sections/thetwo-way/2011/08/11/139536686...
Prisons in the US no doubt have a lot of problems but I don't think Louisiana has any private prisons. And private prisons only hold 8.5% of prisoners across the US.