Few people actually want fentanyl. Some enjoy the patches, but it doesn't have the same feel as heroin/morphine/etc., though they're close enough to all get you high. It's just super cheap and available, illegally. When the cost of the equivalent dose is a tenth or even a quarter, well that's a huge selling point.
As always with opiates, the real issue is improper manufacturing/labeling. Even IV users would be mostly fine if they had properly labelled IV ampoules.
