but sometimes you and a stranger are in a place and circumstances create a reason for you to have a conversation
i dated a girl i met on the dc metro system because i gave up my seat to a tired looking dad and his kid and the only remaining seat was next to her
having done a reasonably pleasant thing in front of her she had some reason to interact with me, and we had a nice five minute chat, then i asked if she was free the one night she hadn't mentioned having plans.
she was clearly not expecting it, had that "is this really happening?" look, but decided to go for it anyway.