Maybe the government believes in the spontaneous generation of drugs?
A couple of quick points, though:
rates of new HIV infections caused by sharing of dirty
needles dropped
This isn't directly connected with the decriminalization. There is a program that allows anyone to switch a used needle by a new one (plus a condom, a bottle cap and instructions) for free in any pharmacy/drug store. This program started years before the decriminalization and had a reduction of HIV infections as a goal (hence the condom and the instructions)One of the main advantages of decriminalization was that is open the doors for a lot more treatments. Before, you had to admit to have committed a crime (with legal consequences) before you could be treated. The decriminalization eliminated these consequences and helped people find the help they needed