Someone else replied already and explained this, though that seems to have attracted a troll of some sort.
Basically, the idea is that people on bikes have better awareness of road conditions as they should be traveling cautiously at lower speeds and aware of their surroundings more than a vehicle driver would be. They can therefore approach an intersection with a stop sign the same way a driver in a car would a yield sign:
1. Slow down, checking for traffic in all other directions
2. If there's no other traffic, proceed without coming to a complete stop
Moreover, it can actually be more dangerous for a bike rider to come to a complete stop. It is much slower for a bike to accelerate from a complete stop than from a slow yield. That puts the bike rider in the intersection for longer, making it more likely that they'll be hit by someone speeding along in another direction, who was out of sight when the biker started. A car in this situation can gun it; a bike rider in a low gear just gets hit.
Next, it's safer on bike riders to take back roads than it is major arteries. In my area, bikers can take the main road with all its traffic and traffic lights, or they can take one of the collector streets in my neighborhood. If they take the main road, they might not have to stop as much, but they are more likely to be hurt in an accident. The neighborhood collector has a lot of stop signs, but if they can treat those as yields then they can take it also without stopping much and be safer due to less overall traffic and slower car speeds.
Finally, not every biker is in tip-top shape. Letting them bike without having to restart from a complete stop as often makes it easier on the biker, which keeps them biking, which is healthier for them and might take a car off the road. For people who don't give a damn about biker safety, but hate sitting in traffic, this benefit is for you.