Our mind doesn't work like this.TrickWithAKnife wrote: This is a city of 13 million people. If you keep seeing the same people over and over, it's convenient, and extremely unlikely.
Just from my recent trip aboard: Were the flight attendant, the women who sold me the ticket to Ueno Zoo and the restaurant waitress who showed me how to write the middle kanji of "Akihabara" the same person? Not likely. Did they look the same, or even similar? In hindsight ... I couldn't tell. They were small young female women with a nice smile and straight black or dark brown hair. Two weeks later, that's all I remember of them. Same goes for the males too - the owner of the Ryokan in Kyoto where I stayed for a few nights and the tram conductor in Hiroshima who explained to me how to pay for the ride were likely very different, but for all I remember them they could as well be twins.
We keep running into the same kind of people, and until and unless they are actually important to us, we only ever remember what kind of person they were. We're doing more or less well at re-recognising them though - humans are great at pattern matching.
So basically, making a generic character sprite - even out without facial characteristics like eyes, mouth or nose! - is fine for those characters, because that's how we end up remembering them anyway.