Good point and well said.
I wonder what kind of bike Sara's boyfriend has? Likewise, what kind of bike were the men riding? If all had Harley Davidsons, I would say there is a pretty decent chance that they at least knew each other by sight.
Though not all Harley owners participate in the biker sub culture, there are plenty that do to varying degrees. Participation ranges from Outlaw / 2% club memberships, to un patched- but leathered up, to charity toy drives, to recreational riding clubs etc.
In my very large urban area, about three bars, say two American Legion clubs and a Harley dealer serve as jumping off points for biker sub culture socializing, charity activities and carousing with antics. A town of 10,000 that would probably have just one jumping off point.