"Life sentence without possibility of parole" is also a thing, but I'm unfamiliar with the technicalities of the law and as such can't say whether or not it's just straight up lying about the possibility of parole.
The system has issues. I'm also one who feels that a (humane, there's no need to get any last-minute revenge boner) execution can be preferable in cases of impossible rehabilitation. Stops them from being an active influence on the other inmates, prevents the possibility of them getting back out (either by escaping or legal loophole), and also doesn't subject them to living the rest of their life behind bars, in an environment that could very well be quite unpleasant for them.
However, as mentioned, the legal system is borked. Not only in that innocents can and do get convicted, but also in that the prison system makes too much money off of having inmates... The longer the better.
Not only do they get those sweet government dollars to just have the person kick around until they die on their own, but they can also be used for slave labor as Ispil pointed out (or rather, how Ispil's point ends up getting skewer by the system as it stands now), squeezing a few more drops of revenue out of an individual. It really wouldn't surprise me to find that executions are deemed as expensive as they are because of some strings pulled to keep a more entrepreneurially-adjusted status quo in place.
It's interesting to note that Norway not only does not have a death penalty, but no prison sentence (lifetime, multiple-lifetime or otherwise) can exceed 23 years. Period. You cannot be incarcerated for longer than 23 years at a time. If you come out and re-offend, then you can of course get a new sentence, but they can't put you away for the rest of your life.
This came up a bit when Breivik (he has since changed his name to Fjotolf Hansen, because the old name had gotten a bit too much negative press for his liking) has his reign of terror in Norway. People were concerned about him eventually hitting the streets again, regardless of the sentence leveled against him, so there was at least one petition going around to instate a death sentence for this one person.
Now, I may not be intrinsically opposed to the death penalty, but that is absolutely not a good idea. We're supposed to have a legal system that people can be judged by, not some committee lynch squad that makes exceptions to the rule.
Since I'm on the subject anyways, might as well mention that he's had a humdinger of a time in prison and has been causing a stink pretty much from the very get-go. He constantly complains about the food, the accommodations, about how he only gets to play on a PS3 and not a PS4 (and how it "doesn't have any fun games"), and he has repeatedly stated that Norway's prison system is by far the most barbaric, inhumane institution of its type in the world.
He also launched a lawsuit against the prison system, saying that the guards were treating him "unfairly" and we're isolating him without due cause (I.E., no offense that warranted solitary confinement). The guards said that yes, they were isolating him... Because if he's left around the other inmates, they'll beat the shit out of him.
He ended up winning the suit and was awarded some concession by the government, I forget what exactly. Fun chap.