I don't know anything about those strips. Do they work only for IV drugs or can they detect fentanyl in pills?
You are right -- those things should be in more plentiful supply. That said, the average heroin junkie is probably unlikely to test their smack. Not that I know any junkies. It just seems to me that if you're jonesing, and you've got a score, and then the strip says there's fentanyl in it -- I mean, addicts wouldn't be addicts if they were able to toss the score because it's unhealthy for them.
My wife had a patient who was seeking medication assisted therapy. He had three friends die from fentanyl ODs in pills. Was he still taking the pills? Yes he was, because he couldn't resist. If there was fentanyl, well he had a good run. Now, he did seek the therapy to try to get off the smack, so he wasn't doing nothing, but he didn't seem to think he could resist even if he knew there was a reasonable chance the pill would be fatal.