Because these organisms [the ideal types of yeast for sourdoughs] always grow on the outside of a fruit or grain, whole grain flours containing the bran will have a much higher microflora count than will white flours, which have very little bran. […] [A] sourdough starter made with white flour will be slower to develop than would one made with whole-grain flour. – Maggie Glezer, “Unraveling Sourdough”, Artisan Baking Across America
Aha! I KNEW there was a good reason that I have insisted on using whole wheat flour to create and feed our starter!
And it is lovely and active. So, naturally (no pun intended), we want to use it to make bread! Because, after all, people were making bread long before jars of commercial yeast were readily available to the general public. And, of course, people continued to make lovely bread without commercial yeast after that time as well.