Doesn't mean you have to engage in unwanted conversation. I've spent many a night in a bar sitting at a lone table or end of the bar nursing a depressing moment. I liked being there because I wasn't alone even though I was. I would have definitely come across as an asshole if anyone had tried to start an unwanted discussion.

I know you're supposed to be social at a bar, but even then I've just had way too many uncomfortable encounters with people.