Prison is not reformation.  It has no benefit other than to temporarily keep your undesirables from view while providing them experiences which will only create even more troubled individuals to be released back into the populace once their time is served.  The best way to eliminate the need for prisons is to improve society to the point where no one is desperate enough to violate laws, this would require changing from the mentality of survival of the fittest to humanity offering its best to all.  This requires changing society from taking what we want to giving to receive. It requires the world to become peaceful and the beings of this planet to actually care about the mothers, daughters, fathers and sons of the human race.  Once you become peaceful, and there are a world of individuals peaceful like you, then world peace will exist.  Until then, the cruelty which surrounds is your fault and the one only to blame is you, hence the need for prisons which you might one day become a guest of whether you believe it possible or not in the name of reformation.