When you verbalize, the first instinct a human has is to engage in the conversation. So when you say, "On your left" or "Passing" or "I think you look marvelous" or "I've got a loaded gun; if you turn around, I'll shoot," a person's first instinct is to turn around and see who's talking to them. If you say a direction such as right or left, they will move in that direction as if it were an order. It's just human nature.

So I got a bell for MUP travel. If there is little traffic, I will ding it a ways off. If I get any reaction or acknowledgment, that's it I'm done and I just ride through. No reaction? I'll ding again as I get closer, and continue to ding the bell until the person makes it apparent they know I'm there and passing on the left. The difference with a bell is that it is impersonal, there is no verbal interaction. Since peds don't have a bell, there is no urge to answer in kind.

Granted, people in the Orient may be more accustomed to crowded situations, but this little video illustrates the concept rather well.