Paralympics and Guide Dogs

Why are there no events that allow guide dogs? The running events for example could easily have guide dogs instead of competitors being handcuffed to able bodied athletes who couldn't cut it in the proper Olympics. I will be competing in the clay pigeon shooting at the London games and we don't allow dogs of any sort despite our long tradition with gun dogs. I am sure the Paralympics would be an ideal opportunity for a new breed of gun guide dogs. Dogs are good swimmers and work well with horses. The possibilities are endless. Changing the subject slightly why don't they have guide dogs for the obese? They could be an invaluable aid running to the chippy or helping take socks off etc.