Life optimizes for the most efficient resource usage. Those deposits were not an efficient source of energy. But life itself is incredible, we have non-oxygen

Life optimizes for the most efficient resource usage. Those deposits were not an efficient source of energy. But life itself is incredible, we have non-oxygen using lifeforms (inefficient, the earliest lifeforms), sulphur-eating lifeforms. Life can use up almost anything, <<if it has to>>. If it doesn't, it just leaves it alone.