I haven't read the book since I was 13 / 14 (ish) and that was some decades ago and not so long after it was first published, by my recollection there was a strong parallel between Spice (must flow) and Oil in a not so subtle way.
Via the Navigators, who lived in dense clouds of spice, transport across the Dune universe was possible - spice was as fundamental to trade and commerce as oil has been here on earth for the past century.
If that recollection was correct, it seems odd to overlook one of the key layers of the original work (as I recall it, of course).