It should be noted ,carrying weight on a bike is whole lot easier than on your body via a backpack.

If you're really hardcore, you'd use your 4 oz. backpack and ride like that, it can't get any lighter. I've seen people do 500 miles ride wit hjust packpack instead of a rack/panniers. I couldn't do it, but for those who can, great for them!

Most of us..... we're in no particular hurry and not overly concerned with counting grams.. The more the merrier