The point that seems to be missed here is that for the mass manufacture of footwear the old hand done operation of attaching soles with pegs was not replaced by a pegging machine but by a sewing machine which is still to this day known as a Blake stitcher. This machine stitches through the outsole and the insole which has the disadvantage of water being able to penetrate the shoe by way of the thread.

The later invention of the Goodyear welt which is sewn to the insole and the upper and protrudes from the bottom of the upper made it possible to make a more water repellant shoe, as the sole is stitched to the welt on the outside of the shoe. Indeed by using 'Veldtschoen' construction and a bellows tongue shoes can be made waterproof.

Sorry to be pedantic, but I have spent many a happy hour resewing new welts into old shoes and do know a little about the subject if not the song.