Passengers are not allowed to bring their own alcohol onto cruise ships. This is because the cruise lines want to control the sale and consumption of alcohol on their ships. They do this for a number of reasons, including safety, liability, and profit.
Safety is a major concern for cruise lines. Alcohol can impair judgment and coordination, which can lead to accidents. Cruise lines do not want to be held liable for accidents that are caused by intoxicated passengers. Liability is another reason why cruise lines do not allow passengers to bring their own alcohol on board. If a passenger becomes intoxicated and causes damage to property or injury to another person, the cruise line could be held liable.