Braiding is not only for the hair. Though used in making bags, it is already called weaving. Braiding gives more strength for whatever it is you wanted to braid. If Rapunzel let down her hair while it was simply let loose, what do you think will happen?
The same is true with braided metal hose. It gives more strength to the hose so whatever goes through will not leak out because the material will not easily break. It also gives easy grasp for the holder even if the hose gets slime all over. You can also see that braiding in cables protecting the inner wires.