They want to die - that would make them martyrs of allah.
They are not having a nice time of it in prison - and besides, they can't suffer when they are dead.
This in spades.
As part of my job, I have met many many people who are in prison for life, and trust me, when it finally hits them they aren't leaving, it's a punishment of living with eternal suffering.
Also - of all the people I met, I don't think any would have stopped during the crime if...