This is because of the European Court of Human Rights that prevents courts from handing hard life sentences. There must be a point when prisoners have to become eligible for parole and have the possibility of being released.
The UK has had issues about this and has had to find a way to adapt: Whole-life ordesr have to be reviewed after some time in order to give a chance of release (at least on paper).
For the same reason, e.g. in France life sentences come with a maximum of 30 years before becoming eligible for parole. What they do is then that they simply keep denying parole for prisoners they want to keep inside.
The UK has had issues about this and has had to find a way to adapt: Whole-life ordesr have to be reviewed after some time in order to give a chance of release (at least on paper).
For the same reason, e.g. in France life sentences come with a maximum of 30 years before becoming eligible for parole. What they do is then that they simply keep denying parole for prisoners they want to keep inside.