Why? Because I want those men to be men, dads. In jail they are on a taxpayer-paid maintenance program to keep them as human scum. Outside in the world, we can bump them into shape.
The Needle park photo is anecdotal photo-propaganda. Such artifacts of more widespread drug use are (1) transitional, and (2) can be almost eliminated by thoughtful preparation for the social transition phase, and by managing that phase much as was done with the Prohibition, in stages.
The gangs of today are fueled by the lack of responsible men. What men there are to the youth who move into gangs are ex-cons.
Keep jail for the violent, the thieves, the extortionists, the bribe makers and bribe takers.
Really?
Now you're moving into the dangerous territory where the corrupted and bought off operate. I want all these scum dragged out into the light of day, no matter how high their positions, explaining their actions to their neighbors and the taxpayers.
Then where would we put Congress?