drugs to money for uncle sam

it is my observation that part of reason, a big part, for some drugs (ex; Marijuana) being illegal is so the more money can be made than if they were legal, and further more these finacial gains would not show up on the books. The us gov has and is doing this. the question is..

if we switch to a cashless society, does our government stand to lose secret cash flow avenues from the sale of drugs?