Saddlebags are simply bags that are attached to the saddles of a vehicle or an animal. Saddles were first used for animals like horses and mules to help the rider get on or off the beast, or to load luggage.
Now, saddlebags have become a trend, especially for bikers. With the fuel price on a steady increase, people are now getting more and more inclined to fuel-less means of transports such as bicycle or vehicles that consume comparatively lesser amounts of fuels like bikes. The only drawback to bicycles and bikes/motorbikes is space. There is just no space to carry any extra luggage. This explains why saddlebags have become almost a necessity for all the bikers.