If making sourdough were 'common sense' then _everyone could do it correctly on their first try_. They don't. Most fail and never try again because the skill level required for sourdough is too high.

I'm an _expert_ cook, but I'm still having to go through the frequent failures of learning how to pickle with brine (fortunately, my failures have been mostly edible and have not turned moldy). Even vinegar pickling requires a certain level of expertise before you can do it successfully, even though that level of expertise is _roughly_ "knowing how to boil water".