They want to make some money out of it. Most of the things that got banned increased their values and I truly believe illegal stuff has more circulation than legal one. Just remembering when China banned Bitcoin it raised in price and popularity.
It seems to me that such a comparison is inappropriate in this case. They could just raise the price, without prohibition. But the government has decided to take it that way, so they want to do to get rid of alcohol. Now it will be sold illegally
Most times, when government makes some decisions, its more haphazard than what they intend for it to achieve. what they do most times is that those decisions are made as a result of bowing to pressures of some set of people who probably are the majority and also for them to be able to appease them and not outrightly because they love the decision. Its their country and they can make any law they so wish to make. Some other country believes that gambling is wrong and they ban it outrightly other places they say if you are not above 18, its ileegal for you among others...