Because drug dealers are people who couldn’t get better jobs. Which suggests they aren’t quite as competent as the lawyers and plumbers and bodyguards who also on occasion kill their rich clients, leading to having a higher rate of the economically unsound activity.

Plus growing up rich is apparently a disability that can get you off a rape charge, so the rich kids are more likely to do the things that you’d kill them over, and drug dealers are more likely to be armed and willing to kill than pizza dealers.