The United States represents about 4.4 percent of the world's population, yet we incarcerate around 22 percent of the world's prisoners.  Non-violent drug offenders comprise 50% of all federal inmates.  In the US each year, there are more than four times as many arrests for drug possession than for drug dealing.  
There are better ways to combat the drug problem in the US than to more aggressively pursue criminal prosecution of non-violent drug offenses, but AG Sessions chooses follow the Trump administration's pattern of creating public policy based on personal biases.