People on the outside learn to live with the bare minimum no matter how hard they work, prisoners shouldn't be given a luxurious life in the name of 'rehabilitation'.
You can rehabilitate someone without giving them special treatment which they do not deserve.
People on the outside struggle to get genuine help when they've done nothing wrong, why should prisoners (and I mean the murdering/paedophile/rapists) get it handed to them on a plate?
This is excluding the fact that many serious offenders are incredibly manipulative and can lie their way to a chosen diagnosis to give themselves an easier sentence, or to convince doctors they are 'sorry' and are 'cured'.
Maybe we should help innocent people before we start pampering prisoners.
Say what you want, there's a reason the Norwegian CJS is one of the most effective in the world. Humane treatment isn't pampering.
It's also worth keeping in mind that this "pampering" works... A 2014 study found that Norway's rate of recidivism was just 20%, compared to the UK's 46% and the US' 52%.
What you're effectively saying is 'throw away all that tax money which could be spent elsewhere (I.E. healthcare) instead of treating people in a humane manor'.