[zkms]

It's not a logical tactic, just, without professional equipment (whose sale is restricted!) working with drugs whose doses are measured in micrograms is a hard task and likely to result in failure.

Why are the drugs in the illicit marketplace the ones with such small active doses? Prohibition strongly incentivises the manufacture/transport/sale of drugs with higher potency (per unit volume) -- as the odds of detection go up with bulkiness: https://en.wikipedia.org/wiki/Iron_law_of_prohibition