In Brave New World, everyone uses drugs to get happy, the drug itself is relatively safe and doesn't hurt productivity, and everyone thinks it's perfectly normal to use drugs.
In the actual world, only a subset of the population uses drugs frequently, only a subset of available drugs can be used without serious side effects (we haven't invented the perfect Soma yet), and there is a lot of moralizing about drug use. Under these circumstances, nothing the government does will make everyone happy, so the government optimizes for the happiness of the voters who matter the most: conservative parents who get all worried about their kids doing ecstasy.
In the actual world, only a subset of the population uses drugs frequently, only a subset of available drugs can be used without serious side effects (we haven't invented the perfect Soma yet), and there is a lot of moralizing about drug use. Under these circumstances, nothing the government does will make everyone happy, so the government optimizes for the happiness of the voters who matter the most: conservative parents who get all worried about their kids doing ecstasy.