Correction: Illegal drugs also cause bad decisions, leading to murder & mayhem. I think the psychological impact of these illegal drugs causes impaired logic function which cannot control primitive emotions. It is a big part of the equation causing the physical violence, the law breaking and the self destruction.
It is true that poverty makes people susceptible to the big tax free money made in the illegal drug market. It does not explain why people take such a big gamble with prison time and loss of life at stake. Nor does it explain why these people are so oblivious to the impact on themselves and those around them.
I believe that the use of these illegal drugs puts people into a grip that destroys their self discipline and the collateral damage takes its course big time due to impaired decision making coupled with the lack of strong moral character. That gamble is taken because poverty and the rules of welfare have made the family unit dysfunctional and unable to build that strong moral character which resists the seduction of drug money and drug use. Take the illegal drugs out of the equation, and people will have a chance to better their lives and the lives around them.
You can clearly see the process of "bad choices" in young children, way before external factors have started to stack up.
A child that is not properly corrected at a young age, will most likely continue to seek immediate gratification into adulthood. What is wired into a child's brain is very difficult to undo.