Law doesn't seek to punish but to rehabilitate. Act of taking freedom away from the criminal is violent enough. Treating them badly is just a sign of unfair/poor society that cannot maintain (afford to keep) it's promise to be civil to all citizens.
Maybe Norway prisons are just really nasty. No drugs, no fights, no conflict with the wardens, just boredom and then solitary confinement if you do anything that's "not OK".