Crack is a byproduct of the drug war.
Because of the harsh penalties for large weights of drugs, and the profit margins involved, it makes economic sense for dealers to offer a highly concentrated, highly compact product at a low unit cost with an extremely high profit margin.
If the penalty was the same for possessing a bottle of wine vs. a bottle of white lightning, which would you sell, bottles of wine or sips of white lightning?
Coca Cola used to have a small quantity of cocaine in every bottle, back when it was "the pause that refreshes."