Indeed. Very few drug users are specifically seeking out fentanyl. It's used as a cheap and potent adulterant that is passed off as more desirable drugs, like prescription opiates, heroin, or even non-opiate type drugs like cocaine. Users are asking for all kinds of drugs and getting fentanyl of variable quantities, either adulterated into or straight up substituted for their intended product, which makes overdosing a real hazard.

Fentanyl adulteration is entirely a black market phenomena.