Whether he poses a danger is not relevant. Punishment, not rehabilitation is the key word here. Simple as that.
Here are a few of these animals today -- marrying, divorcing, producing children, setting up recording studios, taking courses and getting degrees, enjoying conjugal visits and time with their "friends"... Tex Watson even became a "minister." Now there's a guy who really plays the game, but even the bleeding heart shrink who evaluates him considers Watson too dangerous to release.
But.... It's called the "Dept of Corrections" for a reason. Punishment would be way too cheap and wouldn't rip off the taxpayer while also keeping thousands off unemployment.