They’re random people I most likely have never seen before and probably won’t ever see again.

And why do you think that? Have you paid attention to the people around you? If you and another person get to work at the same time, and live in the same area then odds are you will encounter them again. There might be a million people in your city. But how many of them have the exact same commute as you?

Also so what if you never see them again on the train? What if you end up really liking them, get their number, and stay in contact?