For the record I'm not a fan of this sort of censorship either.
But I'm guessing their aversion to drug references is more to avoid offending people than to discourage drug use: opiate (and amphetamine) abuse is a pretty serious problem around the world, and a lot of people have lost family or years of their own lives to addiction. Naming an app after something with so much destructive potential---and as a marketing gimmick, no less---might seem a bit insensitive to some of these people.
Again, I'm not saying I agree with this logic, but it's a perspective to be mindful of.
Genuine question. Is it somehow going to cause more drug use? By what mechanism?
Why do we accept censorship so easily? Is free speech not worth more?