The insane thing is to waste endless money on police and prisons that fail to stop drug abuse while letting people die due to lack of safe injection sites.

It’s entirely possible to both not waste money on police / prisons and to not have injection zones.

It kind of isn’t. This has been studied regarding recidivism and drug use. Rehabilitation and "corrections" are anything but, and are often roadblocks for users trying to get clean, and typically make it more difficult to rejoin society. Due to the insanity of the current system, most people go in and get worse, not better. Harm reduction, on the other hand, cuts out that element, and helps both decriminalize and medicalize the problem. It provides easier routes for people who want to get clean and caps the drug addict to criminal pipeline.

Even if we don't waste money pretending we can "stop" drug use with cops and jails, we still have to pay for the costs associated with overdoses and the spread of disease and a black market. It's cheaper to give someone a clean needle and a test strip than to have them in an ICU bed.

Well sure, ignoring the problem is always an option.