Like with any kind of food which is naturally red - like strawberries, tomatoes, cranberries, pomegranate seeds and red bell peppers - it's a natural anti-oxidant, which helps to detoxify the blood. Also, people can have a bit when they're at a party, or in a pub at a social event, and socializing can be good for someone's emotional well being. Being socially isolated can lead to mental health issues like depression.
Having a little bit of alcohol is fine, as long as someone is staying within the safe limit i.e. no more than 14 units per week for a woman, and no more than 21 units per week for a man. For example, having one single small glass of red wine which is 2 units per day in the evening over the course of a week is okay. The only time it becomes a problem is if someone is drinking to excess, which can result in health issues like liver damage for instance.
Hope this helps.