As someone who's spent a lot of time in San Francisco, I have to say that Bridgeport doesn't remind me of the city at all. I mean, yes, there are docks, but that's true of any city with a shoreline, and both are on a peninsula, but then again so is Pittsburgh in a way (the three rivers making a natural boundary and all that). But aside from downtown office buildings and a few new developments on the east side, SF is overwhelmingly row houses, not apartments. Somehow, even with all the people around, you can still lose yourself completely in any of several parks and forget you're in an urban area at all. And the city proper is built partly across the spine of the north end of a mountain range. Driving is hell on a stick shift, but as you crest over a hill and suddenly catch sight of the water, the view is absolutely spectacular. Even now, it still takes my breath away. To me, Bridgeport captures none of that, although it seems like a fine city in its own right.
As to the other point, most of the big-city stereotypes I'm familiar with are about having fun and avoiding long-term attachments, romantic or otherwise, for as long as possible. Of course there's far too much variety in any real city to get away with broad generalizations, but I think that living in a vibrant place with so many different things to do and people to meet lends itself to exploration and the constant expansion of one's horizons. It makes sense, then, that many young people would lean towards giving themselves a chance to see what's out there before settling into predictable, if happy and comfortable, lives. And, of course, the whole point of a fling is that it's supposed to end.