Your comment and the one to whom you respond show these two points of view. It is interesting that at the moment in the US you have more a "keep the criminals away from the society" point of view and in Europe "try to reintegrate them".
I don't understand that. If we're worried about criminals' integration with society then we shouldn't put them in prison. Prisons exist to separate people from society.
Both by deterring would-be criminals, and by keeping future lawbreakers behind bars where they can't do harm.
Too harsh a punishment often only succeeds in putting someone in a position where they are even more likely to break the law.
E.g. you catch someone for smoking pot, and they get civil service and have to visit social support/psychologist/whatever. This might not do any good but it might do some.
If you send them to jail for 5 years, they it's basically guaranteed that they will get out being in a much worse position than they were before, and more likely do commit crimes.