Can't say for Europe, but in the US, it's expected that inmates will have some sort of job, and that hopefully, they'll learn useful skills from it.

For many years, this was how states mades their car license plates, and in the Southern states, there is a whole culture of prison farms and small entreprises.  Since many US prisions are now managed by the private sector, they really want to make prisoners work, and find ways to boost the profits of the prison corporation.

For more about the privitization of American prisions, see Observer article.  Back in the late 1990's companies that had assumed contracts to run prisons tried to do so on the cheap, and lost control of prisions.  There was quite a bit of what can only be called sadism, and eventually in New Mexico, the state police had to be called in to retake  one of the prisions that this private company lost control of.  Talk about a market failure.

Private companies have absolutely no business running prisions or any other function that involves lending them the legitimate lethal power of the state.

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg