Thing is, people have 'good reason' to want drugs: They feel good, and mostly, people get addicted. Moreover, there is much less of a scale requirement for drugs. It is pretty easy to make money on drugs when 0.1% of all people are using your drugs.
Whereas, a currency used by 0.1% of your friends / neighbors is totally useless.
These reasons make it 1) easier to suppress a currency 2) harder to suppress drugs.