You need a bar for socializing and for a place where Guinan can give you dope advice. People on the Enterprise all rely on each other for survival; everyone hiding in their rooms probably isn't the best for crew morale. Though we do barely see the lives of regular families on board, so maybe they're all shut ins. Self improvement seems to be a big societal thing in the future, though.The replicator effects on society has to be drastic. Why be a bartender in the spaceship when you can be at home with a replicator creating food and videogames for you?
I'm sure there are people who live on Earth and never leave their house and wallow in replicator creations, but such people don't sound like they have the drive to become successful enough to get into Starfleet, much less be stationed on the flagship.