When I was submitting names to BB I had anything with slightly negative connotations rejected, even if the names would have fit particular industries that use those kinds of names (i.e. fashion, creative industries, extreme sports, etc.).
Surprised that cocaine.io got accepted as it's an addictive and illegal drug that kills thousands each year, and have a number of other adverse effects besides overdose. It's certainly more negative than any domain I've gotten rejected. Might have been suitable for a treatment program if it was the .org, but .io is a tech extension, and it seems unlikely that a tech company would try to capitalize on the reputation of a deadly and addictive drug. Especially nowadays when online entities are subject to political correctness and social justice movements, and when big tech companies in general are under fire for their negative impacts on society. Interesting that they suggest that it is suited for anything related to narcotics culture on either side of the divide - not something I would have endorsed if I were them (I assume the two sides of this narcotic drug is education, treatment and prevention on the one hand, and black market sales and usage on the other).