As a vendor from Singapore in a former life pointed out to me, the city-state hangs fewer drug traffickers in one year than a similar sized city in the United States loses to drug related crime and overdose deaths in a single week.
There is a downside. I get the point, but if you are, say, trafficking girls, and you fear that you are on the verge of getting caught, the girls that you have in tow 1) can slow you down, and 2) could be a witness against you. You may make the calculation that getting rid of them is your best option, if you could receive the death penalty either way.