Skyrocketing drink prices are making it too expensive to go out. Smartphone apps mean it's easier for people to stay in touch. Dating apps are cutting out the need to mingle in person. Even larger televisions are allowing friends to stay at home and watch sporting events or movies together. 
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The greatest cause of reduced bar visits has to do with the drinking/driving laws. Nobody wants to spend $20 on taxi rides for a couple of drinks. Folks are just doing their drinking at home. Makes total sense.  I haven't been to a bar for a drink for over 10 years. Maybe 20!