You can't really figure out why drug activity is permitted to continue even when police know what is occurring? Drugs are a major business for not only dealers, but police, lawyers, behavioral health facilities, counselors, correctional officers and the list goes on. A certain level of dealers must remain to keep the stream of addicts. Sure, numbers may rise and fall, but there is no incentive to eradicate. The flip side of this is that with a significant number of the problem troublemakers doped up, they are less likely to cause problems and less problems than those on alcohol.