There are many, many ways to write even a small piece of code/functionality and small sub-optimal choices can lead to tons of entropy down the road. To compound this, almost every solution is going to be different, and there just isn't a '300 Page Manual on Servicing Your Jaguar' equivalent for every possible software solution.

While I get the gist of what you're saying, I think building and repairing physical things is different from building and repairing more abstract things.