As a basic analogy, think of it like human metabolism burning fat vs. carbohydrates. Fat is much more energy dense, but until you starve the body of carbohydra

As a basic analogy, think of it like human metabolism burning fat vs. carbohydrates. Fat is much more energy dense, but until you starve the body of carbohydrates, your body won't burn it. This pathway likely exists as a "backup" metabolic system so that in the absence of easy-to-digest feedstocks, the microbe can still live, but at an energetic cost.