At least two layers to this, of course.
There's the serious addicts, who want to have this reversal drug so they can keep doing whatever they are doing. And I agree - it fixes nothing, really.
Then there are the ones who are caught - and end up with an overdose, maybe not even due to their own choices. The kid who comes home after a party, and then starts ODing on the couch. The reversal drug buys time. Nothing else. Time to get EMTs there, time to get to a hospital. In the medium term, time to possibly get them into rehab or other help. The reversal drug needs to exist. And for some people, it is a life-line. For others... it just makes the mess, messier.
