When training with weapons for the purpose of self defense it makes sense to train with a weapon that you're likely to have at hand. Training with a guandao can be fun and fascinating but in order for it to be useful in self defense you have to have a guandao with you at the time. You're not all that likely to be carrying one around. From my observation, lots of martial arts schools that teach weapons like to teach sticks since sticks are easy to come by. This does make sense. Not everybody trains with weapons with the goal being self defense but if that is your goal I can see why sticks would be a good weapon to train with.