It’s one of the many sins people commit due to selfishness and/or the complete lack of situational awareness. You know who they are: a group of friends that decide the best way to carry on a conversation is to walk, three or four in a row, at a snail’s pace on a busy public sidewalk.
Maybe they think they’re just like those sassy Sex and the City women, and the world is their oyster. Maybe they don’t realize that those women are actresses, and those scenes are shot with extras who are paid to walk three feet behind and not punch them in the back of the head, drag their stunned bodies to the curb and stomp them until they’re dead.