The point of a stop sign is to make people in cars look for traffic before proceeding. Cars approach intersections pretty quickly, and thus can't look for traffic carefully enough unless they slow way down or stop. The stop sign makes sure that every driver does this. Bikes on the other hand, approach intersections more slowly and have the same or more time to look for cross traffic as a car who stops does. I only stop if there actually is cross-traffic to stop for, otherwise there is no reason to.