People buy and sell anything on the black market either for profit or survival; these are two motives so powerful that to authority could reasonably expect to eliminate all actors in such a scenario.
There are several examples of purely-for-profit actions in different
kinds of black markets like the trade of narcotics, conflict diamonds,
weapons and even alcohol that show profusely that no action by part of
any government can erase such transactions completely. Even if violence
is applied on the crackdown there will always be someone willing to take
the risk and play hard against any sort of law for a good profit that
is increased as the risk also rises.
Reality shows that: After hundreds
of deaths and crimes related to the prohibition law, the government of
the United States - the most powerful country on Earth - had to
surrender to the fact that people would still drink alcohol, no matter
what. Not even the Japanese empire could stand against the might of the
U.S. as well as the folks who would like to get drunk sometimes.