Sitting alone, at a nice bar, anywhere in the Bay Area - I could sit there all day, and no one would say a word to me.
Any other city? Even New York? Boston? Austin? Atlanta? Denver? Paris? Berlin? Seattle? No problem. Someone will chat, I'll meet a group, whatever.
Also, I'm extremely social. It's "not me."
Disclaimer: Just an unscientific observation.
However, the odds improve if you avoid "nice" bars - destination bars are a thing, people show up with their group for a few drinks never intending to visit again. They never socialize so locals go elsewhere.
Which is a way of suggesting that it does both ways. I don't know how people develop the skills necessary to approach someone they don't know.
They are all too afraid of “offending” you or committing a “microaggression”. A room full of people all desperate to connect but no one will make the first move in case it ends up on Twitter.
I'm afflicted with a resting bitch face, but if I'm at Zeitgeist in SF, strangers will usually strike up conversation with my party.