No, friend, it is not because we take useless things in our backpack just in case. We do not trust God or other people. There are backpacks that are real storehouses; they have everything. Try to make sure that yours is not like that. It should not weigh more than ten percent of your body weight. And even less is better.
Follow my advice if you like. Fill your backpack with everything you are planning on taking. Then, go take a walk with it one afternoon. When you get home, empty it out and take out whatever weighs too much. If you do this a couple of time, your shoulders and back will definitely thank you. Besides, do you think there are no stores in the towns and cities along the Camino?