Scott,
I think you can make 'beer' out of almost anything natural and organic, straw, grass etc. I think the hops are used to give the unique flavour we are all accustomed to in one of our favourite drinks. If you make it out of something else, you just get a different taste.
My father made 'beer' out of all sorts of things, and they all came out with the same result. You fell over after you had drunk a few cloudy glasses.
Get used to the crappy taste, and you have a very cheap source of neck oil. Perfect for the man (or woman) who had no money to afford the real thing.
In my very early youth, we were one of those very poor families. Dad would brew nettle beer for himself, and we would have a 'ginger beer plant' on a window ledge, that was 'fed' every so often with a spoonful of sugar and a bit more water, the liquid it produced was watered down to make into a cordial, giving us kids the feeling of being able to afford real pop.
You shouldn't knock it, all these old recipes were there to provide succour to the penniless masses, and most times it succeeded.
Bogs