When my commute was further, and I used the train, I'd see the same people every day. I'm not one to strike up a conversation, but I'd say hi to the other bike commuters and occasionally chat about bikes.
Now that my commute is under 4 miles on the most direct route, and it's through mainly residential areas, I don't really see anyone consistently. Every so often I'll time the ride right and bump into my coworkers that also bike commute. The route is a bike route, so there are always folx riding that I'll wave to. More than people though, I notice the same cars parked in the same places.